A production system and method of electronic grade propylene glycol monomethyl ether

Abstract

The present application relates to a kind of electronic grade propylene glycol monomethyl ether production system and method, including from industrial grade propylene glycol monomethyl ether feed to electronic grade propylene glycol monomethyl ether discharge direction in turn cascaded first rectifying tower (1), secondary rectifying tower (2), first micro filter (3), first anion-cation removal device (4), first dehydration tower (5), secondary dehydration tower (6) and nanofilter (7);The first dehydration tower (5) and secondary dehydration tower (6) are connected with azeotrope adding mechanism and azeotrope reflux mechanism.Compared with prior art, the present application provides a kind of electronic grade propylene glycol monomethyl ether production system, the product of the system not only organic impurities and anion-cation reaches electronic grade level, also through the method of adding azeotrope makes the water content in product also reaches the requirement of electronic grade, and the yield of final product is more than 90%.

Description

Technical Field

[0001] This invention relates to the field of propylene glycol monomethyl ether production technology, and in particular to a production system and method for electronic-grade propylene glycol monomethyl ether. Background Technology

[0002] Propylene glycol monomethyl ether (PPD) is a low-toxicity, excellent solvent. Due to its presence of both a lipophilic ether group and a hydrophilic alcohol hydroxyl group, it has wide applications in dissolving both organic and water-soluble substances, earning it the reputation of a "universal" solvent. It is widely used in the chip and semiconductor industries. Currently, the quality standards for PPD mainly test for particle content, anion and cation content, organic matter content, and water content. Organic matter content testing includes, but is not limited to, PPD acetate, 1-methoxy-2-butanol, and ethylene glycol monotert-butyl ether. In industrial production, industrial-grade PPD is typically used to produce electronic-grade PPD. Since PPD and water begin to azeotropically combine at 96.7°C under normal pressure, conventional distillation methods are insufficient to reduce the water content in PPD. Therefore, a low-energy, low-cost, and simple dehydration process is crucial for the successful production of electronic-grade PPD.

[0003] CN 114656339 A uses a partitioned column and membrane filtration method to design a process for electronic-grade propylene glycol monomethyl ether. However, due to the high theoretical plate number of its dehydration column and distillation column, both exceeding 70, the design difficulty and energy consumption in actual industrial production are very high, 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 the separation effect is not good, and the product content is only suitable for use 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 of n-propyl acetate and water is not much different from that of propylene glycol methyl ether and water, it is difficult to produce electronic-grade propylene glycol methyl ether through this process, resulting in a low product yield, 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 intermittent distillation in the process, there are drawbacks such as excessive capacity consumption and high economic costs in actual production. Summary of the Invention

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

[0008] The objective of this invention can be achieved through the following technical solution: 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 and cation remover, a primary dehydration column, a secondary dehydration column, and a nanofilter connected in series from the feed direction of industrial-grade propylene glycol monomethyl ether to the discharge direction of electronic-grade propylene glycol monomethyl ether.

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

[0010] Preferably, the azeotropic agent addition mechanism includes a second microfilter and a second anion and cation remover connected in series.

[0011] The inlet of the second microfilter is fed with an industrial-grade azeotropic agent, and the outlet of the second anion and cation remover is fed with an azeotropic agent to the first-stage dehydration tower and the second-stage dehydration tower.

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

[0013] More preferably, the ratio of the feed amount of the azeotropic agent in the primary dehydration tower to the feed amount of propylene glycol monomethyl ether after the removal of anions and cations is 0.5 to 0.7:1.

[0014] More preferably, the ratio of the feed rate of the azeotropic agent in the secondary dehydration tower to the feed rate of propylene glycol monomethyl ether after the first dehydration is 0.7 to 0.9:1.

[0015] Preferably, the azeotropic agent reflux mechanism includes a distributor;

[0016] The input and output ends of the separator are both connected to the primary dehydration tower and the secondary dehydration tower.

[0017] More preferably, the distributor is a gravity distributor.

[0018] In this invention, the mixture of azeotropic agent and water that comes out from the top of the primary and secondary dehydration towers is cooled and then enters the separator. Since ethyl acetate and water are immiscible, they are separated by gravity separator. Since ethyl acetate has a higher density than water, the azeotropic agent that comes out from the bottom of the separator is returned to the primary and secondary dehydration towers in a ratio of 2 to 4:2.

[0019] Preferably, the azeotropic agent is ethyl acetate. In selecting the azeotropic agent, substances that can form a binary azeotrope with water are preferred, and the boiling point of the binary azeotrope should be less than 10°C lower than the azeotropic temperature of propylene glycol monomethyl ether-water (96.7°C). Considering the recovery of the azeotropic agent, it is desirable to form a heterogeneous azeotrope with water, and in the azeotropic agent recovery tower, a significant difference in volatility between the azeotropic agent and water is desired. Therefore, ethyl acetate is selected as the azeotropic agent for azeotropic distillation in this invention.

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

[0021] Preferably, the number of theoretical plates in the primary and secondary distillation columns is 20 to 30.

[0022] Preferably, the pore size of the microfiltration membrane in the first microfilter is 0.1-0.2 μm.

[0023] Preferably, the pore size of the microfiltration membrane in the second microfilter is 0.1-0.2 μm.

[0024] Preferably, the membrane material of the microfiltration membrane in the first microfilter is selected from one or more of polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, and polycarbonate membrane.

[0025] Preferably, the membrane material of the microfiltration membrane in the second microfilter is selected from one or more of polyamide membrane, polytetrafluoroethylene membrane, polypropylene membrane, and polycarbonate membrane.

[0026] More preferably, the microfiltration membrane material in the first and second microfilters is polytetrafluoroethylene (PTFE). PTFE is resistant to high temperatures, acids and alkalis, has excellent chemical stability, and is strongly hydrophobic.

[0027] Preferably, the material used for the anion and cation exchange resin in the first anion and cation remover is a polystyrene-type exchange resin.

[0028] Preferably, the material used for the cation and anion exchange resins in the second cation and anion remover is a polystyrene-type exchange resin.

[0029] Preferably, the ratio of cation resin to anion resin in the first cation and anion separator is 1:1.5 to 2. More preferably, the ratio of cation resin to anion resin is 1:2, but a ratio of 1:1.5 may be used when the cation content is high.

[0030] Preferably, the ratio of cation resin to anion resin in the second cation and anion separator is 1:1.5 to 2. More preferably, the ratio of cation resin to anion resin is 1:2, but a ratio of 1:1.5 may be used when the cation content is high.

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

[0032] The anion and cation remover of the present invention is placed before the dehydration device in the process flow because the anion and cation exchange resin produces some water after removing the anions and cations from the crude product. This water will be carried out by the anion and cation remover after the crude product from the aforementioned device passes through the anion and cation remover, so it is necessary to install it before the dehydration device.

[0033] Preferably, the theoretical number of trays in the primary dehydration tower and the secondary dehydration tower is 10 to 18.

[0034] Preferably, the pore size of the nanofiltration membrane in the nanofilter does not exceed 10 nm.

[0035] Preferably, the membrane material of the nanofiltration membrane in the nanofilter includes polyvinyl alcohol.

[0036] Preferably, the quality requirements of the industrial-grade propylene glycol monomethyl ether comply with the industry standard "HG / T 3939-2007 Industrial Propylene Glycol Methyl Ether", wherein 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 column 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] More preferably, the temperature of the bottom of the column is higher than the temperature of the top of the column.

[0039] Preferably, the top pressure of the secondary distillation column 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] More preferably, the temperature of the bottom of the column is higher than the temperature of the top of the column.

[0041] Preferably, the pressure at the top of the primary dehydration tower is 0.15-0.25 MPa, the temperature at the top of the tower is 90-100°C, the temperature at the bottom of the tower 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 distributor is 0.08–0.12 MPa and the temperature is 20–30 °C.

[0044] A method for producing electronic-grade propylene glycol monomethyl ether, using the above-mentioned production system, includes the following steps:

[0045] Industrial-grade propylene glycol monomethyl ether is purified by a primary distillation column. The top product is further refined by a secondary distillation column. At the top of the secondary distillation column is a mixture of propylene glycol monomethyl ether and water. The mixture and azeotropic agent are passed separately and sequentially through a microfilter and anion / cation separator before entering the primary dehydration column. The crude product from the bottom of the column and the azeotropic agent that has passed through the microfilter and anion / cation separator are passed into the secondary dehydration column for further dehydration. After passing through a nanofilter, the crude product from the bottom of the column yields the final product, electronic-grade propylene glycol monomethyl ether. The azeotropic agent and water from the top of the primary and secondary dehydration columns are separated by a separator, and the azeotropic agent is refluxed back into the system.

[0046] In this invention, the primary distillation column essentially removes 1-methoxy-2-butanol and ethylene glycol monotert-butyl ether from industrial-grade propylene glycol monomethyl ether, as well as most of the propylene glycol monomethyl ether acetate. In the bottom product of the primary distillation column, 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 distillation column does not treat the water, so the water in the feed will be distilled out from the top of the column along with the propylene glycol monomethyl ether.

[0047] In this invention, the secondary distillation column removes residual propylene glycol monomethyl ether acetate from the propylene glycol monomethyl ether in the aforementioned apparatus, and further reduces the content of other organic impurities. Water is distilled out from the top of the secondary distillation column along with the propylene glycol monomethyl ether. The product exiting from the top of the secondary distillation column contains less than 1 ppm of all organic impurities, including propylene glycol monomethyl ether acetate.

[0048] Because the boiling points of organic impurities in industrial-grade propylene glycol monomethyl ether differ significantly from those of propylene glycol monomethyl ether, they can be largely removed in a single-stage distillation column. Among the organic impurities, the boiling point of propylene glycol monomethyl ether acetate is the smallest compared to that of propylene glycol monomethyl ether. Therefore, a second-stage distillation column is added to the single-stage distillation column to further remove propylene glycol monomethyl ether acetate from the organic impurities. The content of organic impurities in the material exiting the top of the second-stage distillation column is all below 1 ppm.

[0049] In this invention, the azeotropic agent and the crude product from the secondary distillation column are respectively filtered through a microfiltration membrane to remove larger pore size particles from the solution.

[0050] In this invention, the azeotropic agent and the crude product from the secondary distillation column are respectively passed through anion and cation removers to remove the anions and cations from ethyl acetate and propylene glycol monomethyl ether.

[0051] In this invention, the crude product from the anion and cation remover has a metal cation content of less than 100 ppt, which meets the quality requirements for electronic-grade propylene glycol monomethyl ether.

[0052] In this invention, the crude product from the aforementioned device enters the dehydration device. Since propylene glycol monomethyl ether and water form an azeotropic system, the dehydration device uses an azeotropic agent to perform azeotropic distillation.

[0053] In this invention, the crude product from the bottom of the primary dehydration tower has a malonic acid monomethyl ether mass fraction of 99.99%, a water content of less than 100 ppm, and the content of other organic impurities is all below 1 ppm. The crude product from the bottom of the secondary dehydration tower has a malonic acid monomethyl ether mass fraction of more than 99.99% and a water content of less than 50 ppm, which far exceeds the SEMIC12(G4) standard for electronic chemicals.

[0054] The theoretical plate number of both the primary and secondary dehydration towers in this invention is less than 20, which is significantly lower than the more than 50 theoretical plates required in existing technologies. This provides a clear advantage for ethyl acetate as an azeotropic agent in the azeotropic distillation of propylene glycol monomethyl ether and water. The primary and secondary dehydration towers in this dehydration device greatly reduce construction costs and energy consumption, making it highly economical.

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

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

[0057] 2. This invention provides an efficient, energy-saving, and stable production system for producing electronic-grade ultra-clean 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. In this invention, ethyl acetate is used as an azeotropic agent. Compared with cyclohexane, toluene and n-propyl acetate as azeotropic agents, ethyl acetate has a better water-removing ability. Moreover, ethyl acetate and water are different, which makes the recovery of the azeotropic agent more convenient.

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

[0060] 5. The electronic-grade propylene glycol monomethyl ether production apparatus 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%, wherein 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 propylene glycol monomethyl ether product produced by the method of the present invention can achieve a purity of over 99.99%, a metal content of less than 100 ppt, a water content of less than 50 ppm, and a 1-methoxy-2-butanol content of less than 100 ppt.

[0062] 7. The equipment used in the process flow of this invention are all common equipment, suitable for industrial production, with low equipment requirements, low energy consumption and construction costs, and high azeotropic agent recovery rate, which has good economic benefits. Attached Figure Description

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

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

[0065] In the diagram: 1-First-stage distillation column, 2-Second-stage distillation column, 3-First microfilter, 4-First anion and cation remover, 5-First-stage dehydration column, 6-Second-stage dehydration column, 7-Nano filter, 8-Second microfilter, 9-Second anion and cation remover, 10-Separator, 11-Industrial grade propylene glycol monomethyl ether, 12-Propylene glycol monomethyl ether after initial organic matter removal, 13-Primary organic impurities, 14-Propylene glycol monomethyl ether after secondary organic matter removal, 15-Secondary organic impurities, 16-Propylene glycol monomethyl ether after microfiltration, 17-Propylene glycol monomethyl ether after anion and cation removal. 18-Ethyl acetate (industrial grade), 19-Ethyl acetate after microfiltration, 20-Ethyl acetate after removal of anions and cations entering the primary dehydration tower, 21-Mixture of primary water and ethyl acetate, 22-Propylene glycol monomethyl ether after initial dehydration, 23-Ethyl acetate after removal of anions and cations entering the secondary dehydration tower, 24-Mixture of secondary water and ethyl acetate, 25-Propylene glycol monomethyl ether after secondary dehydration, 26-Electronic grade propylene glycol monomethyl ether product, 27-Ethyl acetate refluxed into the primary dehydration tower, 28-Ethyl acetate refluxed into the secondary dehydration tower, 29-Water. Detailed Implementation

[0066] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection 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 industrial-grade propylene glycol monomethyl ether according to national standards is above 99.5% by mass, 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 specifications 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 Industrial Grade Propylene Glycol Monomethyl Ether

[0070] project 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 is as follows: a conventional distillation column, a conventional dehydration column, and a conventional vertical flash tank for the separator.

[0072] Example 1

[0073] A production system for electronic-grade propylene glycol monomethyl ether includes a primary distillation column 1, a secondary distillation column 2, a first microfilter 3, a first anion and cation remover 4, a primary dehydration column 5, a secondary dehydration column 6, and a nanofilter 7, which are connected in series from the feed direction of industrial-grade propylene glycol monomethyl ether to the discharge direction of electronic-grade propylene glycol monomethyl ether.

[0074] Industrial-grade propylene glycol monomethyl ether enters from the primary distillation column 1. Industrial-grade propylene glycol monomethyl ether 11 enters from the primary distillation column 1. Propylene glycol monomethyl ether 12, after initial removal of organic matter by purification in the primary distillation column 1, enters the secondary distillation column 2. Primary organic impurities 13 are collected from the bottom of the column. Propylene glycol monomethyl ether 12, after the initial removal of organic matter, is further purified in a secondary distillation column 2. Secondary organic impurities 15 are collected from the bottom of the column. Propylene glycol monomethyl ether 14, after the second removal of organic matter, enters the first microfilter 3. The microfiltered propylene glycol monomethyl ether 16 enters the first anion and cation remover 4 to remove anions and cations. Propylene glycol monomethyl ether 17, after the removal of anions and cations, enters the primary dehydration column 5. Propylene glycol monomethyl ether 22, after the first dehydration, exits from the bottom of the primary dehydration column 5 and enters the secondary dehydration column 6. Propylene glycol monomethyl ether 25, after the second dehydration, exits from the bottom of the secondary dehydration column 6 and is filtered by a nanofilter 7 to obtain electronic grade propylene glycol monomethyl ether product 26.

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

[0076] Example 2

[0077] A production system for electronic-grade propylene glycol monomethyl ether mainly includes: a distillation column, a microfilter, an anion and cation remover, a dehydration column, a nanofilter, and a separator. The system produces a product with organic impurities and anions and cations reaching electronic-grade levels. Furthermore, by adding an azeotropic agent, the water content in the product also meets electronic-grade requirements, and the final product yield is over 90%.

[0078] The production method of electronic grade propylene glycol monomethyl ether is as follows: Industrial grade propylene glycol monomethyl ether 11 is purified by a primary distillation column 1. Most of the organic impurities (primary organic impurities 13) are collected from the bottom of the column. The top product (propylene glycol monomethyl ether 12 after the first organic removal) is further purified by 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 organic removal) and water. The mixture and azeotropic agent (industrial grade ethyl acetate 18) are passed through microfiltration membranes (first microfilter 3 and second microfilter 8) and cation and anion removers (first cation and anion remover 4 and second cation and anion remover 9) respectively and then enter the primary dehydration column 5 together. The crude product (propylene glycol monomethyl ether 22 after initial dehydration) and the azeotropic agent that has passed through the microfiltration membrane and anion and cation separator are fed into the secondary dehydration tower 6 for further dehydration. The crude product (propylene glycol monomethyl ether 25 after secondary dehydration) exits from the bottom of the tower and passes through the nanofilter 7 to obtain the final electronic grade propylene glycol monomethyl ether product 26. The azeotropic agent and water exiting from the top of the primary dehydration tower 5 and the secondary dehydration tower 6 are separated by the separator 10, and the azeotropic agent is returned to the system. The product has a mass content of 99.99%, with organic impurities in the product all less than 1 ppm and water content less than 50 ppm. The quality of the final product reaches the level of electronic chemical SEMIC12 (G4) and above.

[0079] Example 3

[0080] refer to Figure 1Industrial-grade propylene glycol monomethyl ether 11 was purified by a primary distillation column 1. The primary distillation column 1 has 23 theoretical plates, with partial condensation at the top. The top pressure was 0.2 MPa, the top temperature was 143.2℃, the bottom temperature was 143.6℃, ​​and the reflux ratio was 8. Heavy components were removed. The propylene glycol monomethyl ether at the top (propylene glycol monomethyl ether 12 after the initial organic matter removal) was further purified by a secondary distillation column 2. The secondary distillation column 2 has 25 theoretical plates, with partial condensation at the top. The top pressure was 0.1 MPa, the top temperature was 119.65℃, the bottom temperature was 119.68℃, and the reflux ratio was 7. Heavy components were removed. The propylene glycol monomethyl ether (propylene glycol monomethyl ether 14 after secondary organic matter removal) and azeotropic agent (industrial grade ethyl acetate 18) obtained from the secondary distillation column 2 are sequentially passed through microfiltration membranes (first microfilter 3 and second microfilter 8) to remove particles larger than 0.2 μm. The microfilters are polytetrafluoroethylene membranes with a pore size of 0.2 μm and a uniformity coefficient of 1.13. The azeotropic agent is industrial grade ethyl acetate with a content of 99.8%. After microfiltration, the ions are passed through anion and cation removers (first anion and cation remover 4 and second anion and cation remover 9). The anion and cation removers use ion exchange resins. The resin used is a styrene-type ion exchange resin with particles larger than 0.5 mm and a uniformity coefficient of 1.1. After removing anions and cations, it enters the primary dehydration tower 5. The primary dehydration tower 5 has a theoretical number of 13 plates. Partial condensation is performed at the top of the tower. The top pressure is 0.2 MPa, the top temperature is 98.3℃, the bottom temperature is 143.2℃, and the reflux ratio is 14. Azeotropic distillation of crude propylene glycol monomethyl ether is carried out using ethyl acetate as an azeotropic agent. The bottom product and ethyl acetate are then fed into the secondary dehydration tower 6 for further dehydration. The secondary dehydration tower 6 has a theoretical number of 15 plates. Partial condensation is performed at the top of the tower. The top pressure is 0.2 MPa, and the top temperature is... The temperature at the bottom of the column is 143.25℃, and the reflux ratio is 16. The crude product from the bottom of the column is filtered through nanofilter 7 to remove particles larger than 10nm. The nanofilter 7 membrane can be made of polyvinyl alcohol with a pore size of 10nm and a uniformity coefficient of 1.17. After nanofiltration, the final electronic grade propylene glycol monomethyl ether product 26 is obtained. The mixture of azeotropic agent and water from the top of the primary dehydration column 5 and the secondary dehydration column 6 enters the separator 10 for separation. The pressure inside the separator 10 is 0.1MPa and the temperature is 25℃. The product after passing through the separator is refluxed back to the primary dehydration column 5 and the secondary dehydration column 6, respectively.

[0081] Comparative Example 1

[0082] refer to Figure 2 Compared to Example 3, the reflux device for the azeotropic agent ethyl acetate was not set up, but otherwise it was the same as Example 3.

[0083] Experimental Example 1

[0084] The content of components in propylene glycol monomethyl ether of Example 3 and Comparative Example 1 was determined. The instruments used for detection were: Agilent ICP-MS / MS 8900 for metal elements, boron, silicon, arsenic, etc.; Metrohm 940 ion chromatography for anions; Agilent GC-MS gas chromatography for impurities in raw materials and products; a 851 coulometric cascade titrator for water content; and a RION-KS-19AF particle size analyzer. The results are shown in Table 2.

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

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

[0087]

[0088]

[0089]

[0090] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for producing electronic-grade propylene glycol monomethyl ether, characterized in that, The production system used in this production method includes a primary distillation column (1), a secondary distillation column (2), a first microfilter (3), a first anion and cation remover (4), a primary dehydration column (5), a secondary dehydration column (6), and a nanofilter (7) connected in series from the feed direction of industrial-grade propylene glycol monomethyl ether to the discharge direction of electronic-grade propylene glycol monomethyl ether. The primary dehydration tower (5) and the secondary dehydration tower (6) are connected to an azeotropic agent addition mechanism and an azeotropic agent reflux mechanism; The azeotropic agent addition mechanism includes a second microfilter (8) and a second anion and cation remover (9) connected in series. The inlet of the second microfilter (8) is fed with industrial-grade azeotropic agent, and the outlet of the second anion and cation remover (9) is fed with azeotropic agent to the first-stage dehydration tower (5) and the second-stage dehydration tower (6). The azeotropic agent reflux mechanism includes a distributor (10); The input and output ends of the separator (10) are both connected to the primary dehydration tower (5) and the secondary dehydration tower (6). The industrial-grade azeotropic agent is industrial-grade ethyl acetate; The theoretical number of trays in the primary dehydration tower (5) and the secondary dehydration tower (6) is 10 to 18. The production method includes the following steps: Industrial grade propylene glycol monomethyl ether is purified by a primary distillation column (1), and the propylene glycol monomethyl ether product obtained from the top of the column after the first removal of organic matter is further purified by a secondary distillation column (2). At the top of the secondary distillation column (2) is a mixture of propylene glycol monomethyl ether and water after secondary organic matter removal. The mixture of propylene glycol monomethyl ether and water after secondary organic matter removal is passed through the first microfilter and the first anion and cation remover in sequence, and then enters the primary dehydration column (5) together with a portion of the azeotropic agent that has been processed by the second microfilter (8) and the second anion and cation remover (9) in sequence. The crude propylene glycol monomethyl ether product after initial dehydration from the bottom of the primary dehydration tower (5) is then fed into the secondary dehydration tower (6) along with another portion of the azeotropic agent that has been processed sequentially through the second microfilter (8) and the second anion and cation remover (9) for further dehydration. The crude product after secondary dehydration from the bottom of the secondary dehydration tower (6) is filtered through a nanofilter (7) to obtain the final product, electronic grade propylene glycol monomethyl ether. The azeotropic agent and water from the top of the primary dehydration tower (5) and the secondary dehydration tower (6) are separated by a separator (10), and then the azeotropic agent is returned to the primary dehydration tower and the secondary dehydration tower respectively.

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

3. The method for producing electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The microfiltration membrane in the first microfilter (3) has a pore size of 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.

4. The method for producing electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The material used for the cation and anion exchange resins in the first cation and anion remover (4) is polystyrene-type exchange resin, and the filling ratio of cation resin to anion resin is 1:1.5~2.

5. The method for producing electronic-grade propylene glycol monomethyl ether according to claim 1, characterized in that, The nanofiltration membrane in the nanofilter (7) has a pore size of no more than 10 nm and the membrane material includes polyvinyl alcohol.

Images