Production system and method of electronic-grade propylene glycol monomethyl ether

Abstract

The invention relates to a production system and method of electronic-grade propylene glycol monomethyl ether. The production system comprises a primary rectifying tower (1), a secondary rectifying tower (2), a first micro-filter (3), a first anion and cation remover (4), a primary dehydrating tower (5), a secondary dehydrating tower (6) and a nano-filter (7) which are sequentially connected in series in the direction from industrial-grade propylene glycol monomethyl ether feeding to electronic-grade propylene glycol monomethyl ether discharging. And the first-stage dehydrating tower (5) and the second-stage dehydrating tower (6) are connected with an entrainer adding mechanism and an entrainer reflux mechanism. Compared with the prior art, the electronic-grade propylene glycol monomethyl ether production system provided by the invention has the advantages that not only are organic impurities and zwitterions in the product of the system reach the electronic grade, but also the water content in the product also reaches the electronic grade requirement by a method of adding the entrainer, and the yield of the final product is 90% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of propylene glycol monomethyl ether production, and in particular to a production system and method for electronic-grade propylene glycol monomethyl ether. Background Art

[0002] Propylene glycol monomethyl ether is an excellent solvent with low toxicity. Due to the presence of two functional groups, a lipophilic ether group and a hydrophilic alcohol hydroxyl group, it has a wide range of applications in the dissolution of organic substances and water-soluble substances, and is hailed as a "universal" solvent, with relatively many applications in the fields of chips and semiconductors. At present, the detection contents of the quality standard of propylene glycol monomethyl ether mainly include particle content, anion and cation content, organic matter content, water content, etc. Among them, the detection of organic matter content includes but is not limited to propylene glycol monomethyl ether acetate, 1-methoxy-2-butanol, and ethylene glycol monoter-butyl ether. In industrial production, industrial-grade propylene glycol monomethyl ether is usually used to produce electronic-grade propylene glycol monomethyl ether. Since propylene glycol monomethyl ether and water start to azeotrope at 96.7 °C under normal pressure, it is difficult to reduce the water content in propylene glycol monomethyl ether using conventional distillation operations. A water removal process with low energy consumption, low cost, and simple operation is the key to the quality of the technology for producing electronic-grade propylene glycol monomethyl ether.

[0003] CN 114656339 A uses the method of a dividing wall column and membrane filtration to design the process for electronic-grade propylene glycol monomethyl ether. However, due to the excessively high number of theoretical plates in its dehydration column and distillation column, both being above 70, the design difficulty in actual industry and the energy consumption in production are very large, which is not conducive to industrial implementation.

[0004] CN 103449981 A uses cyclohexane as an azeotropic agent to separate propylene glycol monomethyl ether and water, but its separation effect is not good, and the product content can only be used as industrial-grade propylene glycol monomethyl ether and cannot be used for the production of electronic grade.

[0005] CN 216170042 U uses n-propyl acetate as an azeotropic agent to separate propylene glycol methyl ether and water. However, since the azeotropic temperature formed by n-propyl acetate and water is not much different from the azeotropic temperature of propylene glycol methyl ether and water, it is very difficult to produce electronic-grade propylene glycol methyl ether through this process, and the product yield is too low, which is not conducive to industrial production.

[0006] CN 216777948 U uses cyclopentanone as an azeotropic agent to separate propylene glycol methyl ether and water. However, due to the use of batch distillation in the process, there are defects such as excessive production capacity consumption and high economic cost in actual production. Summary of the Invention

[0007] The purpose of the present invention is to provide a production system and method for electronic-grade propylene glycol monomethyl ether.

[0008] The object of the present invention can be achieved by the following technical solutions: A production system for electronic-grade propylene glycol monomethyl ether, comprising a primary distillation column, a secondary distillation column, a first microfilter, a first anion-cation remover, a primary dehydration tower, a secondary dehydration tower, and a nano-filter connected in series in the direction from the feeding of industrial-grade propylene glycol monomethyl ether to the discharging of electronic-grade propylene glycol monomethyl ether;

[0009] The primary dehydration tower and the secondary dehydration tower are connected with an azeotropic agent adding mechanism and an azeotropic agent reflux mechanism.

[0010] Preferably, the azeotropic agent adding mechanism comprises a second microfilter and a second anion-cation remover connected in series in turn;

[0011] The industrial-grade azeotropic agent is input at the inlet end of the second microfilter, and the azeotropic agent is output from the outlet end of the second anion-cation remover to the primary dehydration tower and the secondary dehydration tower.

[0012] More preferably, the feeding amount of the azeotropic agent in the primary dehydration tower is not less than 150 kg / h, and the feeding amount of the azeotropic agent in the secondary dehydration tower is not less than 100 kg / h.

[0013] Even more preferably, the ratio of the feeding amount of the azeotropic agent in the primary dehydration tower to the feeding amount of propylene glycol monomethyl ether after removing anions and cations is 0.5 - 0.7:1.

[0014] Even more preferably, the ratio of the feeding amount of the azeotropic agent in the secondary dehydration tower to the feeding amount of propylene glycol monomethyl ether after the first dehydration is 0.7 - 0.9:1.

[0015] Preferably, the azeotropic agent reflux mechanism comprises a liquid separator;

[0016] Both the input end and the output end of the liquid separator are connected to the primary dehydration tower and the secondary dehydration tower.

[0017] More preferably, the liquid separator is a gravity liquid separator.

[0018] In the present invention, the mixture of the azeotropic agent and water coming out from the tops of the primary dehydration tower and the secondary dehydration tower enters the liquid separator after being cooled. Since ethyl acetate and water are immiscible, a gravity liquid separator is used to separate them. The density of ethyl acetate is greater than that of water. Therefore, the azeotropic agent coming out from the bottom of the liquid separator will be refluxed to the primary dehydration tower and the secondary dehydration tower respectively in a ratio of 2 - 4:2.

[0019] Preferably, the azeotropic agent is ethyl acetate. In terms of selecting the azeotropic agent, substances that can form a binary azeotrope with water are preferably chosen. The boiling point of the binary azeotrope should be 10°C or lower than the azeotropic temperature of propylene glycol monomethyl ether - water, which is 96.7°C. Considering the recovery of the azeotropic agent, on the one hand, it is desired to form a heterogeneous azeotrope with water, and on the other hand, in the azeotropic agent recovery column, a large volatility difference with water is desired. Therefore, ethyl acetate is selected as the azeotropic agent used in azeotropic distillation in the present invention.

[0020] Preferably, the industrial - grade azeotropic agent is industrial - grade ethyl acetate. The quality requirements for industrial - grade ethyl acetate specified in the national standard "GB / T 3728 - 2007 Ethyl Acetate for Industrial Use" are that the mass fraction of ethyl acetate is above 99.7%, and the mass fraction of water is below 0.05%. The mass fraction of ethyl acetate used in the present invention needs to be higher than 97%. The quality requirements for industrial - grade ethyl acetate far exceed the requirements of the present invention.

[0021] Preferably, the number of theoretical plates of the first distillation column and the second distillation column is 20 - 30.

[0022] Preferably, the pore diameter of the micro - filtration membrane in the first micro - filter is 0.1 - 0.2 μm.

[0023] Preferably, the pore diameter of the micro - filtration membrane in the second micro - filter is 0.1 - 0.2 μm.

[0024] Preferably, the membrane material of the micro - filtration membrane in the first micro - filter is selected from one or more of polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, and polycarbonate membrane.

[0025] Preferably, the membrane material of the micro - filtration membrane in the second micro - filter is selected from one or more of polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, and polycarbonate membrane.

[0026] More preferably, the micro - filtration membrane materials in the first micro - filter and the second micro - filter are polytetrafluoroethylene. Polytetrafluoroethylene is heat - resistant, acid - and alkali - resistant, has excellent chemical stability, and has strong hydrophobicity.

[0027] Preferably, the material of the cation - anion exchange resin in the first cation - anion remover is polystyrene - type exchange resin.

[0028] Preferably, the material of the cation - anion exchange resin in the second cation - anion remover is polystyrene - type exchange resin.

[0029] Preferably, the filling ratio of cation resin to anion resin in the first cation-anion remover is 1:1.5 - 2. Preferably, the filling ratio of cation resin to anion resin is 1:2, but the filling ratio of 1:1.5 will also be used when the cation content is relatively high.

[0030] Preferably, the filling ratio of cation resin to anion resin in the second cation-anion remover is 1:1.5 - 2. Preferably, the filling ratio of cation resin to anion resin is 1:2, but the filling ratio of 1:1.5 will also be used when the cation content is relatively high.

[0031] Preferably, the first cation-anion remover and the second cation-anion remover are of synchronous regeneration type.

[0032] In the process flow of the present invention, the cation-anion remover is arranged before the dehydration device. This is because after the cation-anion exchange resin removes the cations and anions in the crude product, some water is generated. The water will be carried out by the crude product coming out of the aforementioned device after passing through the cation-anion remover. Therefore, it needs to be installed before the dehydration device.

[0033] Preferably, the number of theoretical plates of the primary dehydration tower and the secondary dehydration tower is 10 - 18.

[0034] Preferably, the pore diameter of the nano-filtration membrane in the nano-filter does not exceed 10 nm.

[0035] Preferably, the membrane material of the nano-filtration membrane in the nano-filter includes polyvinyl alcohol.

[0036] Preferably, the quality requirements of industrial-grade propylene glycol monomethyl ether comply with the industry standard "HG / T 3939-2007 Propylene Glycol Methyl Ether for Industrial Use". The mass fraction of propylene glycol monomethyl ether is above 99.5%, the mass fraction of 2-methoxy-1-propanol is below 0.4%, and the mass fraction of water is below 0.1%.

[0037] Preferably, the top pressure of the primary distillation tower is 0.15 - 0.25 MPa, the top temperature is 140 - 150 °C, the bottom temperature is 140 - 150 °C, and the reflux ratio is 7 - 9.

[0038] Further preferably, the bottom temperature is higher than the top temperature.

[0039] Preferably, the top pressure of the secondary distillation tower is 0.08 - 0.12 MPa, the top temperature is 110 - 130 °C, the bottom temperature is 110 - 130 °C, and the reflux ratio is 6 - 8.

[0040] Further preferably, the bottom temperature is higher than the top temperature.

[0041] Preferably, the top pressure of the primary dehydration tower is 0.15 - 0.25 MPa, the top temperature is 90 - 100 °C, the bottom temperature is 140 - 150 °C, and the reflux ratio is 12 - 16.

[0042] Preferably, the top pressure of the secondary dehydration tower is 0.15 - 0.25 MPa, the top temperature is 90 - 110 °C, the bottom temperature is 140 - 150 °C, and the reflux ratio is 14 - 18.

[0043] Preferably, the pressure inside the liquid separator is 0.08 - 0.12 MPa, and the temperature is 20 - 30 °C.

[0044] A production method of electronic-grade propylene glycol monomethyl ether is carried out using the above production system, and it includes the following steps:

[0045] Purify industrial-grade propylene glycol monomethyl ether through a primary rectification tower, and further refine the top product through a secondary rectification tower. At the top of the secondary rectification tower is a mixture of propylene glycol monomethyl ether and water. The mixture and the entrainer are respectively and sequentially passed through a microfilter and an anion-cation remover and then enter the primary dehydration tower together. The crude product coming out from the bottom of the tower and the entrainer that has passed through the microfilter and the anion-cation remover are introduced into the secondary dehydration tower for further dehydration. After the crude product comes out from the bottom of the tower and passes through a nano-filter, the final product, electronic-grade propylene glycol monomethyl ether, can be obtained. The entrainer and water coming out from the tops of the primary dehydration tower and the secondary dehydration tower are separated by a liquid separator, and the entrainer is refluxed into the system.

[0046] In the present invention, the primary rectification tower basically removes 1-methoxy-2-butanol and ethylene glycol monoter-butyl ether in industrial-grade propylene glycol monomethyl ether, as well as most of the propylene glycol monomethyl ether acetate. In the bottom product of the primary rectification tower, the content of organic impurities is below 1 ppm, and the content of propylene glycol monomethyl ether acetate is between 20 - 50 ppm. The primary rectification tower does not treat water, so the water in the raw material will distill out from the top of the tower along with propylene glycol monomethyl ether.

[0047] In the present invention, the secondary rectification tower removes the remaining propylene glycol monomethyl ether acetate in the propylene glycol monomethyl ether in the aforementioned device, and also further reduces the content of other organic impurities. Water will distill out from the top of the rectification tower along with propylene glycol monomethyl ether in the secondary rectification tower. The content of all organic impurities including propylene glycol monomethyl ether acetate in the product coming out from the top of the secondary rectification tower is lower than 1 ppm.

[0048] Since the boiling points of the organic impurities in industrial-grade propylene glycol monomethyl ether differ significantly from that of propylene glycol monomethyl ether, they can be basically removed completely in the primary distillation column. Among the organic impurities, the boiling point of propylene glycol monomethyl ether acetate has the smallest difference from that of propylene glycol monomethyl ether. Therefore, a secondary distillation column is added on the basis of the primary distillation column to further remove propylene glycol monomethyl ether acetate in the organic impurities. The content of organic impurities in the material coming out from the top of the secondary distillation column is below 1 ppm.

[0049] In the present invention, the entrainer and the crude product coming out from the secondary distillation column are respectively passed through a microfiltration membrane to remove particulate matters with larger pore diameters in the solution.

[0050] In the present invention, the entrainer and the crude product coming out from the secondary distillation column are respectively passed through an anion-cation remover to remove anions and cations in ethyl acetate and propylene glycol monomethyl ether.

[0051] In the present invention, the content of metal cations in the crude product coming out from the anion-cation remover is below 100 ppt, meeting the quality requirements of electronic-grade propylene glycol monomethyl ether.

[0052] In the present invention, the crude product coming out from the aforesaid device enters the dehydration device. Since there is an azeotropic system between propylene glycol monomethyl ether and water, the dehydration device adopts the method of adding an entrainer to carry out azeotropic distillation.

[0053] In the present invention, the mass fraction of monomethyl malonate in the crude product coming out from the bottom of the primary dehydration column reaches 99.99%, the water content is less than 100 ppm, and the content of other organic impurities is below 1 ppm. The mass fraction of monomethyl malonate in the crude product coming out from the bottom of the secondary dehydration column exceeds 99.99%, the water content is less than 50 ppm, far exceeding the SEMIC12(G4) standard of electronic chemicals.

[0054] In the dehydration device of the present invention, the number of theoretical plates of both the primary dehydration column and the secondary dehydration column is less than 20, which is significantly reduced compared with the more than 50 theoretical plates required in the prior art. Using ethyl acetate as the entrainer in the azeotropic distillation of propylene glycol monomethyl ether and water has obvious advantages. The primary dehydration column and the secondary dehydration column in the dehydration device greatly reduce the construction cost and energy consumption requirements, and have strong economy.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The present invention provides a production system for electronic-grade propylene glycol monomethyl ether. The product of this system not only meets the electronic-grade levels in terms of organic impurities and anions and cations, but also the water content in the product meets the electronic-grade requirements by adding an entrainer method, and the yield of the final product is above 90%.

[0057] 2. The present invention provides a production system for efficiently, energy-savingly and stably producing electronic-grade ultra-high-purity propylene glycol monomethyl ether from industrial-grade propylene glycol monomethyl ether. The obtained electronic-grade propylene glycol monomethyl ether can be used as a solvent, dispersant and diluent in industries such as semiconductors, panels, photovoltaics, cellulose, and acrylates.

[0058] 3. The present invention uses ethyl acetate as an azeotropic agent. Compared with using cyclohexane, toluene and n-propyl acetate as azeotropic agents, using ethyl acetate has better water-carrying ability, and ethyl acetate and water are immiscible with each other, which will be more convenient for the recovery of the azeotropic agent.

[0059] 4. The present invention uses a process from microfiltration to anion-cation separator to nanofiltration to remove particulate matter and metal cations in industrial-grade propylene glycol monomethyl ether, so that the final product meets the quality of electronic chemicals SEMIC12 (G4) and above.

[0060] 5. The production device of electronic-grade propylene glycol monomethyl ether of the present invention can purify industrial-grade propylene glycol monomethyl ether with a mass content of 99.5% to electronic-grade propylene glycol monomethyl ether with a mass content of 99.99%. The content of organic impurities in the product is less than 1 ppm, and the water content is less than 50 ppm.

[0061] 6. The mass content of the propylene glycol monomethyl ether product produced by the method of the present invention can reach more than 99.99%, the metal content is below 100 ppt, the water content is below 50 ppm, and the content of 1-methoxy-2-butanol is below 100 ppt.

[0062] 7. All the equipment used in the technological process of the present invention are common equipment, suitable for industrial production, with low requirements for equipment conditions, less energy consumption and construction costs, and high azeotropic agent recovery rate, having good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a schematic diagram of the production method of the production system of electronic-grade propylene glycol monomethyl ether of the present invention.

[0064] Figure 2 It is a schematic diagram of the production method of the production system of propylene glycol monomethyl ether in Comparative Example 1.

[0065] In the figure: 1 - primary rectification column, 2 - secondary rectification column, 3 - first micro filter, 4 - first anion and cation remover, 5 - primary dehydration column, 6 - secondary dehydration column, 7 - nano filter, 8 - second micro filter, 9 - second anion and cation remover, 10 - liquid distributor, 11 - industrial grade propylene glycol monomethyl ether, 12 - propylene glycol monomethyl ether after the first removal of organic substances, 13 - primary organic impurities, 14 - propylene glycol monomethyl ether after the second removal of organic substances, 15 - secondary organic impurities, 16 - propylene glycol monomethyl ether after micro filtration, 17 - propylene glycol monomethyl ether after removal of anions and cations, 18 - industrial grade ethyl acetate, 19 - ethyl acetate after micro filtration, 20 - ethyl acetate entering the primary dehydration column after removal of anions and cations, 21 - mixture of primary water and ethyl acetate, 22 - propylene glycol monomethyl ether after the first dehydration, 23 - ethyl acetate entering the secondary dehydration column after removal of anions and cations, 24 - mixture of secondary water and ethyl acetate, 25 - propylene glycol monomethyl ether after the second dehydration, 26 - electronic grade propylene glycol monomethyl ether product, 27 - ethyl acetate refluxing into the primary dehydration column, 28 - ethyl acetate refluxing into the secondary dehydration column, 29 - water. Detailed implementation mode

[0066] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0067] The raw materials used in the following examples and comparative examples are industrial grade propylene glycol monomethyl ether. The purity of the national standard industrial grade propylene glycol monomethyl ether is above 99.5% by mass content, the content of 2 - methoxy - 1 - propanol is below 0.4%, the content of water is below 0.1%, and the content of acid is below 0.01%.

[0068] The indicators of the industrial grade propylene glycol monomethyl ether used in the following examples and comparative examples are shown in Table 1.

[0069] Table 1 Indicators of raw material industrial grade propylene glycol monomethyl ether

[0070] Item Index Mass fraction of propylene glycol monomethyl ether / % 99.5 Other organic impurities / ppm 1127 Water / ppm 502

[0071] The equipment used in the following examples: the rectification column selects a conventional rectification column, the dehydration column selects a conventional rectification column, and the liquid distributor selects a conventional vertical flash tank.

[0072] Example 1

[0073] A production system for electronic grade propylene glycol monomethyl ether includes a primary rectification column 1, a secondary rectification column 2, a first micro filter 3, a first anion and cation remover 4, a primary dehydration column 5, a secondary dehydration column 6, and a nano filter 7 connected in series in sequence from the feeding of industrial grade propylene glycol monomethyl ether to the discharging of electronic grade propylene glycol monomethyl ether.

[0074] Industrial - grade propylene glycol monomethyl ether enters from the first - stage rectification tower 1, and industrial - grade propylene glycol monomethyl ether 11 enters from the first - stage rectification tower 1. The propylene glycol monomethyl ether 12 after the first removal of organic substances obtained by purifying through the first - stage rectification tower 1 enters the second - stage rectification tower 2, and the primary organic - matter impurities 13 are drawn from the bottom of the tower. The propylene glycol monomethyl ether 12 after the first removal of organic substances is further refined in the second - stage rectification tower 2, and the secondary organic - matter impurities 15 are drawn from the bottom of the tower. The propylene glycol monomethyl ether 14 after the second removal of organic substances at the top of the tower enters the first micro - filter 3, and the micro - filtered propylene glycol monomethyl ether 16 obtained enters the first anion - cation remover 4 to remove anions and cations. The propylene glycol monomethyl ether 17 after removing anions and cations enters the first - stage dehydration tower 5. The propylene glycol monomethyl ether 22 after the first dehydration coming out from the bottom of the first - stage dehydration tower 5 enters the second - stage dehydration tower 6. The propylene glycol monomethyl ether 25 after the second dehydration coming out from the bottom of the second - stage dehydration tower 6 is filtered through a nano - filter 7 to obtain an electronic - grade propylene glycol monomethyl ether product 26.

[0075] Moreover, in the system of this embodiment, there are also an azeotropic agent adding mechanism and an azeotropic agent reflux mechanism. The azeotropic agent adding mechanism includes a second micro - filter 8 and a second anion - cation remover 9, and the azeotropic agent reflux mechanism includes a liquid separator 10. Industrial - grade ethyl acetate 18 is processed by the second micro - filter 8 to obtain micro - filtered ethyl acetate 19. The micro - filtered ethyl acetate 19 is processed by the second anion - cation remover 9 to obtain ethyl acetate 20 entering the first - stage dehydration tower after removing anions and cations and ethyl acetate 23 entering the second - stage dehydration tower after removing anions and cations, which are used as azeotropic agents for azeotropic distillation with propylene glycol monomethyl ether. The mixture of primary water and ethyl acetate 21 at the top of the first - stage dehydration tower 5 and the mixture of secondary water and ethyl acetate 24 at the top of the second - stage dehydration tower 6 are separated by the liquid separator 10 to obtain ethyl acetate 27 flowing back into the first - stage dehydration tower, ethyl acetate 28 flowing back into the second - stage dehydration tower, and water 29.

[0076] Example 2

[0077] A production system for electronic - grade propylene glycol monomethyl ether mainly includes: a rectification tower, a micro - filter, an anion - cation remover, a dehydration tower, a nano - filter, and a liquid separator. The products of this system not only meet the electronic - grade levels in terms of organic impurities and anions and cations, but also achieve the electronic - grade requirements for the water content in the products by adding an azeotropic agent method, and the yield of the final product is above 90%.

[0078] The production method of electronic-grade propylene glycol monomethyl ether is as follows: Industrial-grade propylene glycol monomethyl ether 11 is purified through a primary distillation column 1, and most of the organic impurities (primary organic impurities 13) are withdrawn from the bottom of the column. The overhead product (propylene glycol monomethyl ether 12 after the first removal of organic substances) is further refined through a secondary distillation column 2. At the top of the secondary distillation column 2 is a mixture of propylene glycol monomethyl ether (propylene glycol monomethyl ether 14 after the second removal of organic substances) and water. The mixture and the azeotropic agent (industrial-grade ethyl acetate 18) are respectively and sequentially passed through microfiltration membranes (the first microfilter 3, the second microfilter 8) and anion-cation removers (the first anion-cation remover 4, the second anion-cation remover 9) and then enter a primary dehydration column 5 together. The crude product (propylene glycol monomethyl ether 22 after the first dehydration) coming out from the bottom of the column and the azeotropic agent that has passed through the microfiltration membrane and the anion-cation remover are introduced into a secondary dehydration column 6 for further dehydration. The crude product (propylene glycol monomethyl ether 25 after the second dehydration) comes out from the bottom of the column and can obtain the final electronic-grade propylene glycol monomethyl ether product 26 after passing through a nano-filter 7. The azeotropic agent and water coming out from the tops of the primary dehydration column 5 and the secondary dehydration column 6 are separated by a liquid separator 10, and the azeotropic agent is refluxed into the system. The mass content of the product is 99.99%, the content of organic impurities in the product is less than 1 ppm, and the water content is less than 50 ppm. The quality of the final product reaches the level of electronic chemical SEMIC12 (G4) and above.

[0079] Example 3

[0080] Reference Figure 1, industrial-grade propylene glycol monomethyl ether 11 is purified through a primary rectification column 1. The primary rectification column 1 has 23 theoretical plates. Partial condensation is carried out at the top of the column. The top pressure is 0.2 MPa, the top temperature is 143.2 °C, the bottom temperature is 143.6 °C, and the reflux ratio is 8. Heavy components are removed. The propylene glycol monomethyl ether at the top of the column (propylene glycol monomethyl ether 12 after the first removal of organic substances) is further refined through a secondary rectification column 2. The secondary rectification column 2 has 25 theoretical plates. Partial condensation is carried out at the top of the column. The top pressure is 0.1 MPa, the top temperature is 119.65 °C, the bottom temperature is 119.68 °C, and the reflux ratio is 7. Heavy components are removed. The propylene glycol monomethyl ether (propylene glycol monomethyl ether 14 after the second removal of organic substances) and the azeotropic agent (industrial-grade ethyl acetate 18) obtained from the secondary rectification column 2 sequentially pass through microfiltration membranes (the first microfilter 3, the second microfilter 8) to remove particles larger than 0.2 μm (micrometers). The microfilter uses a polytetrafluoroethylene membrane with a pore size of 0.2 μm (micrometers) and a uniformity coefficient of 1.13. The azeotropic agent uses industrial-grade ethyl acetate, and the content of ethyl acetate is 99.8%. After microfiltration, it passes through anion-cation removers (the first anion-cation remover 4, the second anion-cation remover 9). The anion-cation remover uses ion exchange resin. The ion exchange resin is particles larger than 0.5 mm and has a uniformity coefficient of 1.1 styrene-type exchange resin. After removing anions and cations, it enters a primary dehydration column 5. The primary dehydration column 5 has 13 theoretical plates. Partial condensation is carried out at the top of the column. The top pressure is 0.2 MPa, the top temperature is 98.3 °C, the bottom temperature is 143.2 °C, and the reflux ratio is 14. The azeotropic agent ethyl acetate is used for azeotropic distillation of crude propylene glycol monomethyl ether. The bottom product and the azeotropic agent ethyl acetate enter a secondary dehydration column 6 together for further dehydration. The secondary dehydration column 6 has 15 theoretical plates. Partial condensation is carried out at the top of the column. The top pressure is 0.2 MPa, the top temperature is 100.72 °C, the bottom temperature is 143.25 °C, and the reflux ratio is 16. The crude product coming out from the bottom of the column is filtered by a nano filter 7 to remove particles larger than 10 nm (nanometers). The nano filter 7 membrane can use a polyethylene glycol with a pore size of 10 nm (nanometers) and a uniformity coefficient of 1.17. After nanofiltration, the final electronic-grade propylene glycol monomethyl ether product 26 can be obtained. The mixture of the azeotropic agent and water coming out from the tops of the primary dehydration column 5 and the secondary dehydration column 6 enters a separator 10 together for separation. The pressure inside the separator 10 is 0.1 MPa and the temperature is 25 °C. The products after passing through the separator are respectively refluxed to the primary dehydration column 5 and the secondary dehydration column 6.

[0081] Comparative Example 1

[0082] Reference Figure 2 , compared with Example 3, there is no reflux device for the azeotropic agent ethyl acetate, and the others are the same as Example 3.

[0083] Test Example 1

[0084] The components in the propylene glycol monomethyl ether of Example 3 and Comparative Example 1 were detected for their contents. The detection instruments were as follows: for product metal elements and elements such as boron, silicon, and arsenic, Agilent ICP-MS / MS 8900 was used; for anions, Metrohm 940 ion chromatography was used; for the impurity contents of raw materials and products, Agilent GC-MS gas chromatography was used; for water content, 851 type Coulometric Karl Fischer titrator was used; and for particle size analyzer, RION-KS-19AF was used. The results are shown in Table 2.

[0085] The product specifications of the electronic-grade propylene glycol monomethyl ether obtained in Example 3 and Comparative Example 1 are shown in Table 2.

[0086] Table 2 Product Specifications of Electronic-Grade Propylene Glycol Monomethyl Ether

[0087]

[0088]

[0089]

[0090] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A production system for electronic-grade propylene glycol monomethyl ether, characterized in that, it includes a primary distillation column (1), a secondary distillation column (2), a first microfilter (3), a first anion-cation remover (4), a primary dehydration column (5), a secondary dehydration column (6) and a nanofiltration membrane (7) connected in series in the direction from industrial-grade propylene glycol monomethyl ether feed to electronic-grade propylene glycol monomethyl ether discharge; The primary dehydration column (5) and the secondary dehydration column (6) are connected with an azeotropic agent adding mechanism and an azeotropic agent reflux mechanism.

2. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The azeotropic agent adding mechanism includes a second microfilter (8) and a second anion-cation remover (9) connected in series; The inlet end of the second microfilter (8) inputs industrial-grade azeotropic agent, and the outlet end of the second anion-cation remover (9) outputs azeotropic agent to the primary dehydration column (5) and the secondary dehydration column (6).

3. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The azeotropic agent reflux mechanism includes a liquid distributor (10); Both the input end and the output end of the liquid distributor (10) are connected to the primary dehydration column (5) and the secondary dehydration column (6).

4. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The industrial-grade azeotropic agent is industrial-grade ethyl acetate.

5. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The number of theoretical plates of the primary distillation column (1) and the secondary distillation column (2) is 20 - 30.

6. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The pore diameter of the microfiltration membrane in the first microfilter (3) is 0.1 - 0.2 μm, and the membrane material is selected from one or more of polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, and polycarbonate membrane.

7. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The materials of the anion-cation exchange resins in the first anion-cation remover (4) are polystyrene-type exchange resins, and the filling ratio of cation resin to anion resin is 1:1.5 - 2.

8. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The number of theoretical plates of the primary dehydration column (5) and the secondary dehydration column (6) is 10 - 18.

9. The production system for electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The pore diameter of the nanofiltration membrane in the nanofiltration membrane (7) does not exceed 10 nm, and the membrane material includes polyvinyl alcohol.

10. A production method for electronic-grade propylene glycol monomethyl ether, characterized in that, it is carried out by using the production system according to any one of claims 1 - 9, and includes the following steps: Purify industrial-grade propylene glycol monomethyl ether through a primary distillation column (1). The overhead product is further refined through a secondary distillation column (2). At the top of the secondary distillation column (2) is a mixture of propylene glycol monomethyl ether and water. The mixture and the entrainer are respectively and sequentially passed through a microfilter and an anion-cation remover and then enter a primary dehydration column (5) together. The crude product coming out from the bottom of the column and the entrainer that has passed through the microfilter and the anion-cation remover are introduced into a secondary dehydration column (6) for further dehydration. After the crude product comes out from the bottom of the column and passes through a nano-filter (7), the final product, electronic-grade propylene glycol monomethyl ether, can be obtained. The entrainer and water coming out from the tops of the primary dehydration column (5) and the secondary dehydration column (6) are separated by a liquid separator (10), and the entrainer is refluxed into the system.

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