Method for producing high-purity electronic-grade methanol by using industrial-grade methanol

Abstract

The invention relates to a method for producing high-purity electronic-grade methanol by using industrial-grade methanol. The method comprises the following steps: removing organic impurities and water in a methanol raw material through primary rectification, carrying out microfiltration to preliminarily remove particle impurities, removing zwitterions, carrying out secondary rectification to further remove organic impurities and water, and carrying out nanofiltration to further remove particle impurities. Compared with the prior art, the method has the advantages of high product purity, high process yield, low impurity content, strong process continuity and the like, and the produced electronic-grade methanol product meets SEMI C12 and above standards, so that the method has a relatively strong industrial prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanol production, and relates to a method for producing high-purity electronic-grade methanol from industrial-grade methanol. Background Art

[0002] Electronic-grade methanol is mainly used in the electronic cleaning industry, and is often used as a cleaning agent, degreasing agent and desiccant for semiconductors, silicon crystal solar cells, liquid crystal panels and ultra-large scale integrated circuits. Its cleanliness and purity have an important impact on the yield, electrical performance and reliability of integrated circuits. With the improvement of the integrated circuit manufacturing process, higher requirements are also put forward for the methanol product indicators supporting it. Based on the SEMI C12 standard formulated by the International Organization for Semiconductor Equipment and Materials, the main body purity of the product should be greater than 99.8%, the water content should be less than 50 ppm, the metal cation content should be less than 100 ppt, the anion content should be less than 50 ppb, and the particle size should be controlled below 0.2 μm. High-purity methanol is usually purified from industrial-grade methanol as raw material, and the combination of distillation and other separation means is the main purification means. Distillation usually adopts a multi-stage distillation method, and other separation means include adsorption, filtration and ion exchange, etc. Based on the publicly available patent literature, China faces some challenges in the production field of high-purity methanol. For example, the product indicators of most processes cannot reach the SEMI C12 and above standards and cannot meet the requirements of the current integrated circuit processing technology. Second, industrial-grade methanol often contains impurities such as acetone that are easy to form azeotropes with methanol, and conventional distillation means cannot effectively separate methanol and acetone. Third, the existing patents lack effective and feasible control means for important indicators of the process flow, such as product yield and device energy consumption, and thus are not suitable for industrial promotion.

[0003] Chinese Patent Document CN102875326A discloses a method for preparing high-purity anhydrous methanol by azeotropic-adsorption method. This method uses ethyl acetate as an azeotropic agent and ATBS copolymer as an adsorbent material. Specifically, a methanol raw material with a water content of 4.5-5.5 wt% and an azeotropic agent are added to a reactor for azeotropic distillation, and then the anhydrous methanol intermediate is heated and passed through an adsorption column filled with ATBS copolymer medium under the conditions of 35-40 °C and 0.4-0.6 MPa to prepare a high-purity anhydrous methanol product, whose methanol purity reaches more than 99.95 wt% and the content of impurity metal ions is lower than 50 ppm. However, this method only mentions the control means for the content of impurity metal ions and does not involve the control means for the content of solid particles, and the product indicators cannot reach the SEMI C12 and above standards.

[0004] Chinese Patent Document CN101250088A discloses a method for continuous production of high-purity methanol. Specifically, industrial-grade methanol is mixed with a metal ion complexing agent (ethylenediaminetetraacetic acid) accounting for 0.5 - 1 wt% of the methanol raw material in a pre-processor, filtered, and then successively passed through a rectification column, a cation and anion exchange device, and a nano-filter to obtain a high-purity methanol product. The content of each single cation is less than 1 ppb, the content of each single anion is less than 100 ppb, and the number of particles larger than 0.5 μm is less than 5 / mL. Although this patent adopts a continuous process flow and effectively controls the content of solid particles in methanol, the product index of the prepared methanol only reaches the SEMI C8 standard and cannot meet the SEMI C12 and above standards.

[0005] Chinese Patent Document CN109678667A discloses a method for separating and purifying crude methanol. This method uses multi-stage rectification to produce high-purity methanol. Specifically, the methanol raw material passes through a pre-separation column, and extractive distillation is carried out with dimethyl sulfoxide or glycerol as the extractant to remove low-boiling substances in the methanol raw material to obtain pre-separated methanol, and then successively passes through a pressurized column and a main rectification column to obtain a high-purity methanol product. However, this method does not provide an effective means for recycling the bottom mixed liquid rich in the extractant, and direct discharge is likely to cause environmental pollution and loss of the extractant.

[0006] Chinese Patent Document CN10745817A discloses a method for separating acetone-methanol azeotrope using an ionic liquid as an extractant. This method uses 1-ethyl-3-methylimidazolium dicyanamide as the extractant, overcomes the difficulties of separating methanol-acetone azeotrope using traditional rectification means, and realizes the efficient separation of methanol and acetone. At the same time, this method regenerates and recycles the ionic liquid, reducing environmental pollution and loss of the extractant.

[0007] Chinese Patent Document CN11470958A discloses a method and device for producing high-purity electronic-grade methanol. Specifically, 95 wt% industrial-grade methanol is used as the raw material. First, most of the water in the methanol is removed through a dehydration processor, then the large solid particles in the methanol are removed through a micro-filter, and then the anions and cations in the methanol are removed through an anion and cation remover. The methanol from which anions and cations are removed is further passed through a dehydration processor to remove a small amount of water and organic impurities in the raw material, and finally, solid fine particles are removed through a nano-filter. This method can prepare a high-purity methanol product with a purity of up to 99.99%, with a water content of less than 20 ppm, an impurity metal ion content of less than 100 ppt, and no more than 200 solid particles with a particle size larger than 0.2 μm (micrometer) per mL, meeting the SEMI C12 and above standards. However, this method does not mention effective means for controlling the methanol yield in the process flow, and its industrial feasibility remains to be verified. Summary of the Invention

[0008] The object of the present invention is to provide a method for producing high-purity electronic-grade methanol from industrial-grade methanol, which has the advantages of high product purity, high process yield, low impurity content, strong process continuity, etc. The produced electronic-grade methanol product meets the SEMI C12 and above standards and has strong industrialization prospects.

[0009] The object of the present invention can be achieved by the following technical solutions:

[0010] A method for preparing ultra-high-purity methanol, characterized in that it includes primary rectification to remove organic impurities and water in the methanol raw material, microfiltration to preliminarily remove particulate impurities, anion and cation removal, secondary rectification to further remove organic impurities and water, and nanofiltration to further remove particulate impurities.

[0011] Further, the primary rectification is achieved through a first separator, and the first separator includes a first de-light tower and a first de-heavy tower arranged in series, and the bottom discharge port of the first de-light tower is connected to the feed port of the first de-heavy tower.

[0012] Further, the number of theoretical plates of the first de-light tower and the first de-heavy tower is 10 - 50, the operating pressure is atmospheric pressure or slightly positive pressure, the top temperature is 60 - 70 °C, and the reflux ratio is 1 - 15.

[0013] Further, the first de-light tower is an extractive distillation tower, and a flash tank is also provided between the first de-light tower and the first de-heavy tower. The heavy component discharge port of the flash tank is connected to the first de-light tower, and the light component discharge port is connected to the feed port of the first de-heavy tower.

[0014] Considering the methanol-acetone azeotropic system, after the industrial-grade methanol raw material containing acetone impurities enters the first de-light tower of the first-stage separator, part of the methanol will be lost from the top due to the methanol-acetone azeotropic system. At the same time, part of the acetone will also remain in the methanol mixture withdrawn from the bottom of the tower. Ionic liquid, as a new type of green solvent, has almost no volatility, is easy to recycle, and has excellent chemical stability and thermal stability. Using ionic liquid as an extractant can break the methanol-acetone azeotropic system, better remove acetone from methanol, and reduce the loss of methanol at the same time.

[0015] In some preferred embodiments, the methanol raw material enters the first de - light tower of the first - stage separator, and the extractant is added at a position close to the top (preferably the 2nd - 3rd tray from the top of the tower). The light - component impurity acetone is taken out from the top of the tower, and the methanol, extractant, water, and other heavy - component impurities are taken out from the bottom of the tower. The mixed liquid taken out from the bottom of the tower enters the extractant regeneration device to recover the extractant. The extractant regeneration device can be a flash tank. The high - purity extractant taken out from the bottom of the flash tank returns to the first de - light tower for reuse, and the methanol from which the extractant has been removed taken out from the top of the flash tank enters the first de - heavy tower. The extractant can be a single ionic liquid or a mixture of multiple ionic liquids. The cation of the ionic liquid used can be imidazole - based, pyridine - based, quinoline - based, quaternary ammonium salt - based, etc., and the anion can be halogen, acetate, tetrafluoroborate, hexafluorophosphate, phosphate ester - based, etc.

[0016] Further, the number of theoretical plates of the extractive distillation column is 10 - 50, the operating pressure is atmospheric pressure or slightly positive pressure, the top - tower temperature is 50 - 70 °C, and the reflux ratio is 1 - 10.

[0017] Further, the operating temperature of the flash tank is 60 - 350 °C.

[0018] Further, during the microfiltration process, the pore size of the filter membrane used is 0.1 - 0.2 μm (micrometer); during the nanofiltration process, the pore size of the filter membrane used is 10 - 50 nm (nanometer).

[0019] In some preferred embodiments, the materials of the microfiltration membrane and the nanofiltration membrane are one or several of polytetrafluoroethylene, polyimide, polyamide, polyvinylidene fluoride (PVDF) membrane, polyethersulfone membrane, or other membranes with the same properties.

[0020] Further, during the process of removing cations and anions, the ion - exchange medium used is one or several of sulfonic - group styrene resin, quaternary - amine - group styrene resin, sulfonated polyethersulfone resin, or perfluorosulfonic acid resin.

[0021] Further, the re - rectification is achieved through the second separator. The second separator includes a second de - light tower and a second de - heavy tower arranged in series, and the bottom discharge port of the second de - light tower is connected to the feed port of the second de - heavy tower.

[0022] In some preferred embodiments, the inner lining of the second de - light tower and the second de - heavy tower is polytetrafluoroethylene.

[0023] Further, after the top discharge of the second de - light tower and the bottom discharge of the second de - heavy tower are mixed, they are returned to the first de - light tower. Considering that in the second - stage separator, the waste liquid taken out from the top of the second de - light tower and the waste liquid taken out from the bottom of the second de - heavy tower are rich in methanol, the two streams are mixed and recycled as raw materials.

[0024] Furthermore, the number of theoretical plates of the second light component removal column and the second heavy component removal column is 10 - 50, the operating pressure is atmospheric pressure or slightly positive pressure, the top temperature is 60 - 70 °C, and the reflux ratio is 1 - 15.

[0025] Compared with the prior art, the present invention has the following characteristics:

[0026] 1) The present invention uses industrial-grade methanol as the raw material, with a methanol purity of 99.5 wt%. First, most of the water and organic impurities in the raw material are removed through the first-stage separator. Then, the solid large particles in the methanol are removed through a microfilter. The methanol after microfiltration continues to remove most of the anions and cations through an anion-cation remover. The obtained methanol enters the next-stage separator to remove the water generated during the ion exchange process and further remove the organic impurities in the raw material. Finally, the methanol withdrawn from the separator passes through a nanofiltration membrane to remove the solid fine particles in the methanol, obtaining high-purity methanol with a purity meeting 99.99 wt%, a metal ion content below 100 ppt, and no more than 200 solid particles with a particle size greater than 0.2 μm per mL. It has the advantages of high product purity, high process yield, low impurity content, and strong process continuity, realizing the production of high-purity electronic-grade methanol products meeting the SEMI C12 and above standards from industrial-grade methanol raw materials, thus meeting the demand for high-purity electronic-grade methanol in industries such as semiconductors and having strong industrialization prospects;

[0027] 2) The present invention uses conventional distillation or extractive distillation to preliminarily remove the organic impurities and water in the raw material methanol. At the same time, in the extractive distillation process, the ionic liquid 1,3-dimethylimidazolium acetate is used as the extractant to break the methanol-acetone azeotropic system, reducing the loss of methanol at the top of the column while separating acetone, thereby improving the yield and purity of methanol;

[0028] 3) The present invention adopts a cyclic design, that is, the waste liquid withdrawn from the top of the second light component removal column rich in methanol and the waste liquid withdrawn from the bottom of the second heavy component removal column are mixed and recycled as raw materials to the first light component removal column for reuse, thereby reducing the loss of methanol in the overall process flow and further improving the yield of methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of a production device for a high-purity electronic-grade methanol in Example 1;

[0030] Figure 2 is a schematic structural diagram of a production device for a high-purity electronic-grade methanol in Example 2;

[0031] Figure 3 is a schematic structural diagram of a production device for a high-purity electronic-grade methanol in Comparative Example 1;

[0032] Figure 4It is a schematic structural diagram of a production device for a high-purity electronic-grade methanol in Comparative Example 2;

[0033] Description of the markings in the figure:

[0034] 1 - Methanol raw material, 2 - First light removal tower, 3 - Light component discharge from the first light removal tower, 4 - Heavy component discharge from the first light removal tower, 5 - Flash tank, 6 - Methanol with [MMIM][Ac] removed, 7 - Regenerated high-purity [MMIM][Ac], 8 - First heavy removal tower, 9 - Methanol taken from the top of the first heavy removal tower, 10 - Heavy component discharge from the first heavy removal tower, 11 - Microfilter, 12 - Methanol after microfiltration, 13 - Anion and cation remover, 14 - Methanol after removing anions / cations, 15 - Second light removal tower, 16 - Overhead product of the second light removal tower, 17 - Bottom product of the second light removal tower, 18 - Second heavy removal tower, 19 - Methanol taken from the top of the second heavy removal tower, 20 - Bottom product of the second heavy removal tower, 21 - Nanofiltration membrane, 22 - High-purity methanol product. 23 - Recirculating mixed liquid rich in methanol Specific embodiments

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented on the premise of the above technical solutions of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process temperatures not mentioned in the following embodiments are all at room temperature.

[0036] As Figure 1 shown, a production device for high-purity electronic-grade methanol includes a first-stage separator, a microfilter 11, an anion and cation remover 13, a second-stage separator, and a nanofiltration membrane 21. It is used to produce a high-purity methanol product with a purity meeting 99.99 wt%, a metal ion content below 100 ppt, and no more than 200 solid particles with a particle size greater than 0.2 μm per mL. The present invention provides a production method for high-purity electronic-grade methanol with high product purity, low impurity content, high process yield, strong process continuity, and strong industrialization prospects. It realizes the production of high-purity methanol products meeting the SEMI C12 and above standards from industrial-grade methanol raw materials, so as to meet the demand for high-purity electronic-grade methanol in industries such as semiconductors.

[0037] Industrial-grade methanol raw material 1 enters the first de-light tower 2 and the first de-heavy tower 8 of the first-stage separator to remove most of the water and organic impurities in the raw material. The first-stage separator can adopt a series of polished stainless-steel conventional distillation towers. The methanol 9 drawn from the top of the first de-heavy tower enters a microfilter 11 to remove solid particles with a particle size of more than 0.2 μm in the methanol. The microfilter can adopt one or several of polytetrafluoroethylene, polyimide, polyamide, polyvinylidene fluoride membrane, polyethersulfone membrane with a pore size of 0.1 - 0.2 μm or other membranes with the same properties. The microfiltered methanol 12 enters an anion-cation remover 13 to remove anion and cation impurities. The ion exchange medium of the anion-cation remover 13 can be one or several of sulfonic acid group styrene resin, quaternary amine group styrene resin, sulfonated polyethersulfone resin, perfluorosulfonic acid resin. The methanol further removes water and organic impurities through the second de-light tower 15 and the second de-heavy tower 18 of the second-stage separator, and the bottom product 17 of the second de-light tower is fed into the second de-heavy tower 18. The second-stage separator can adopt a series of conventional distillation towers with a polytetrafluoroethylene lining to avoid the introduction of impurity metal ions. Finally, the methanol passes through a nanofiltration membrane 21 to remove solid particles with a size of more than 50 nm. The nanofiltration membrane can adopt one or several of polytetrafluoroethylene, polyimide, polyamide, polyvinylidene fluoride membrane, polyethersulfone membrane with a pore size of 10 - 50 nm or other membranes with the same properties. Finally, a high-purity methanol product with a purity meeting 99.99 wt%, a metal ion content below 100 ppt, and no more than 200 solid particles with a particle size greater than 0.2 μm per mL is obtained.

[0038] Meanwhile, after the overhead product 16 of the second de-light tower and the bottom product 20 of the second de-heavy tower are mixed and subjected to heat exchange, a recycled mixed liquid 23 rich in methanol is obtained and used as a raw material to enter the first de-light tower 2 for recycling.

[0039] The methanol raw material in the present invention is industrial-grade methanol. The purity of national standard industrial-grade methanol is above 99 wt%. The specific raw material composition is shown in Table 1.

[0040] Table 1 Composition of industrial-grade methanol raw material

[0041]

[0042] The ultra-high purity methanol in the present invention refers to high-purity methanol with a purity meeting 99.99 wt%, a metal ion content below 100 ppt, and no more than 200 solid particles with a particle size greater than 0.2 μm per mL.

[0043] Example 1:

[0044] Reference Figure 1, the industrial-grade methanol raw material 1 enters the first-stage separator. This separator uses two conventional distillation columns made of polished stainless steel - the first light-removing tower 2 and the first heavy-removing tower 8. Among them, the top pressure of the first light-removing tower 2 is 0.12 MPa, the top temperature is 60 °C, the bottom temperature is 75 °C, the number of theoretical plates is 30, the reflux ratio is 11, the feeding position of the methanol raw material 1 is the 15th tray, the light components of the first light-removing tower are drawn from the top as 3, and the heavy components of the first light-removing tower are drawn from the bottom as 4 and sent to the first heavy-removing tower 8; the top pressure of the first heavy-removing tower 8 is 0.12 MPa, the top temperature is 68 °C, the bottom temperature is 75 °C, the number of theoretical plates is 30, the feeding position is the 15th tray, the reflux ratio is 3, and the heavy components of the first heavy-removing tower are drawn from the bottom as 10. After removing most of the water and organic impurities, the methanol 9 drawn from the top of the first heavy-removing tower enters the microfilter 11 to remove solid particles with a particle size above 0.2 μm. The filter membrane of the microfilter uses a polytetrafluoroethylene membrane with a pore size of 0.2 μm and a uniformity coefficient of 1.1. The microfiltered methanol 12 removes anionic and cationic impurities through the ion-exchange resin in the anion-cation remover 13 to obtain methanol 14 after removing anions / cations, and then enters the second-stage separator to further remove water and organic impurities. The second-stage separator uses two conventional distillation columns with a polytetrafluoroethylene lining - the second light-removing tower 15 and the second heavy-removing tower 18. Among them, the top pressure of the second light-removing tower 15 is 0.12 MPa, the top temperature is 60 °C, the bottom temperature is 73 °C, the number of theoretical plates is 15, the feeding position is the 8th tray, and the reflux ratio is 10. The top pressure of the second heavy-removing tower 18 is 0.12 MPa, the top temperature is 68 °C, the bottom temperature is 73 °C, the number of theoretical plates is 15, the feeding position is the 8th tray, and the reflux ratio is 2. The methanol product 19 drawn from the top of the second heavy-removing tower removes solid particles with a particle size above 10 nm through the nanofiltration membrane 21. The filter membrane of the nanofiltration membrane 21 uses a polyvinylidene fluoride membrane with a pore size of 10 nm and a uniformity coefficient of 1.25. After nanofiltration, high-purity methanol product 22 is obtained, and the specific indicators are shown in Table 2.

[0045] Meanwhile, after the overhead product 16 of the second light-removing tower and the bottom product 20 of the second heavy-removing tower are mixed and passed through heat exchange, a circulating mixed liquid 23 rich in methanol is obtained and used as a raw material to enter the first light-removing tower 2 for recycling, and the feeding position is the 15th tray.

[0046] Example 2:

[0047] Reference Figure 2, the industrial-grade methanol raw material 1 enters the first-stage separator. The separator uses two conventional distillation columns made of polished stainless steel - the first light-component removal tower 2 and the first heavy-component removal tower 8. Among them, the first light-component removal tower 2 adopts extractive distillation, and the extractant is the ionic liquid 1,3-dimethylimidazolium acetate [MMIM][Ac]. The top pressure of the tower is 0.12 MPa, the top temperature is 70 °C, the bottom temperature is 80 °C, the number of theoretical plates is 30, the reflux ratio is 9, and the feeding position of the methanol raw material 1 is the 15th tray. [MMIM][Ac] is added as the extractant from the 3rd tray of the first light-component removal tower 2, and the solvent ratio is 0.3. Light-component impurities such as acetone are taken out from the top of the tower, denoted as the light-component discharge 3 of the first light-component removal tower. A mixed liquid containing methanol, [MMIM][Ac], water, and other heavy-component impurities is taken out from the bottom of the tower, denoted as the heavy-component discharge 4 of the first light-component removal tower. The heavy-component discharge 4 of the first light-component removal tower enters the extractant regeneration device. The extractant regeneration device uses a flash tank 5 with an operating pressure of 0.05 MPa and an operating temperature of 100 °C. The regenerated high-purity [MMIM][Ac] 7 is returned to the first light-component removal tower 2 for recycling, and the methanol 6 from which [MMIM][Ac] has been removed continues to enter the first heavy-component removal tower 8. The first heavy-component removal tower 8 adopts conventional distillation. The top pressure of the tower is 0.12 MPa, the top temperature is 70 °C, the bottom temperature is 76 °C, the number of theoretical plates is 30, the feeding position is the 15th tray, and the reflux ratio is 3. After removing most of the water and heavy-component impurities, the methanol 9 taken out from the top of the first heavy-component removal tower enters a microfilter 11 to remove solid particles with a particle size of more than 0.2 μm (micrometer). The filter membrane of the microfilter can use a polytetrafluoroethylene membrane with a pore size of 0.2 μm (micrometer) and a uniformity coefficient of 1.1. The microfiltered methanol 12 removes anionic and cationic impurities through the ion-exchange resin of the anion-cation remover 13 and then enters the second-stage separator to further remove water and organic impurities. The second-stage separator can use two conventional distillation columns with a polytetrafluoroethylene lining - the second light-component removal tower 15 and the second heavy-component removal tower 18. Among them, the top pressure of the second light-component removal tower 15 is 0.12 MPa, the top temperature is 60 °C, the bottom temperature is 75 °C, the number of theoretical plates is 15, the feeding position is the 8th tray, and the reflux ratio is 10. The top pressure of the second heavy-component removal tower 18 is 0.12 MPa, the top temperature is 70 °C, the bottom temperature is 75 °C, the number of theoretical plates is 15, the feeding position is the 8th tray, and the reflux ratio is 2. The methanol 19 taken out from the top of the second heavy-component removal tower passes through a nanofiltration membrane 21 to remove solid particles with a particle size of more than 10 nm (nanometer). The filter membrane of the nanofiltration membrane can use a polyvinylidene fluoride membrane (PVDF) with a pore size of 10 nm (nanometer) and a uniformity coefficient of 1.25. After nanofiltration, high-purity methanol product 22 is obtained, and the specific indicators are shown in Table 2.

[0048] Meanwhile, after the overhead product 16 from the second light component removal column 15 and the bottom product 20 from the second heavy component removal column 18 are mixed and then undergo heat exchange, a recycled mixed liquid 23 rich in methanol is obtained and enters the first light component removal column 2 as raw material for recycling, with the feeding position being the 15th tray.

[0049] Comparative Example 1:

[0050] Reference Figure 3 , compared with Example 1, the waste liquid recycling device for the second light component removal column 15 and the second heavy component removal column 18 is not provided, and the others are the same as those in Example 1. The product indexes are shown in Table 2. Compared with Example 1, the methanol recovery rate is relatively low.

[0051] Comparative Example 2:

[0052] Reference Figure 4 , compared with Example 2, the waste liquid recycling device for the second light component removal column 15 and the second heavy component removal column 18 is not provided, and the others are the same as those in Example 2. The product indexes are shown in Table 2. Compared with Example 2, the methanol recovery rate is relatively low.

[0053] Test Example 1:

[0054] The components in the methanol of Examples 1 - 2 and Comparative Examples 1 - 2 are detected for their contents. The detection instruments are as follows: for product metal elements and elements such as boron, silicon, and arsenic, Agilent ICP - MS / MS 8900 is used; for anions, Metrohm 940 ion chromatography is used; for the impurity contents of raw materials and products, Agilent GC - MS gas chromatography is used; for water content, 851 type Coulometric Karl Fischer titrator is used; for particle size analyzer, RION - KS - 19AF is used. The results are shown in Table 1 and Table 2.

[0055] Table 2 Product indexes obtained by the present invention

[0056]

[0057]

[0058] The above table is to illustrate the components contained in industrial - grade methanol raw materials, and does not limit the applicability of the present invention. The purity of the methanol product produced by the patented invention method can reach 99.99 wt%, the metal ion content is below 100 ppt, and the number of solid particles with a particle size greater than 0.2 μm (micrometer) does not exceed 200 per mL, meeting the SEMI C12 and above standards.

[0059] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention as disclosed should be within the protection scope of the present invention.

Claims

1. A purification method for ultra-high purity methanol, characterized in that, it includes primary rectification to remove organic impurities and water in the methanol raw material, microfiltration to preliminarily remove particulate impurities, anion and cation removal, secondary rectification to further remove organic impurities and water, and nanofiltration to further remove particulate impurities.

2. The purification method for ultra-high purity methanol according to claim 1, characterized in that, the primary rectification is achieved through a first separator, and the first separator includes a first light removal tower (2) and a first heavy removal tower (8) arranged in series, and the bottom discharge port of the first light removal tower (2) is connected to the feed port of the first heavy removal tower (8).

3. The purification method for ultra-high purity methanol according to claim 2, characterized in that, the number of theoretical plates of the first light removal tower (2) and the first heavy removal tower (8) is 10 - 50, the top temperature is 60 - 70 °C, and the reflux ratio is 1 - 15.

4. The purification method for ultra-high purity methanol according to claim 2, characterized in that, the first light removal tower (2) is an extractive distillation tower, and the extractant used is 1,3 - dimethylimidazolium acetate. A flash tank (5) is also provided between the first light removal tower (2) and the first heavy removal tower (8). The heavy component discharge port of the flash tank (5) is connected to the first light removal tower (2), and the light component discharge port is connected to the feed port of the first heavy removal tower (8).

5. The purification method for ultra-high purity methanol according to claim 4, characterized in that, the number of theoretical plates of the extractive distillation tower is 10 - 50, the top temperature is 50 - 70 °C, and the reflux ratio is 1 - 10.

6. The purification method for ultra-high purity methanol according to claim 1, characterized in that, during microfiltration, the pore size of the filter membrane used is 0.1 - 0.2 μm; during nanofiltration, the pore size of the filter membrane used is 10 - 50 nm.

7. The purification method for ultra-high purity methanol according to claim 1, characterized in that, during anion and cation removal, the ion exchange medium used is one or several of sulfonic acid group styrene resin, quaternary amine group styrene resin, sulfonated polyethersulfone resin or perfluorosulfonic acid resin.

8. The purification method for ultra-high purity methanol according to claim 2, characterized in that, the secondary rectification is achieved through a second separator, and the second separator includes a second light removal tower (15) and a second heavy removal tower (18) arranged in series, and the bottom discharge port of the second light removal tower (15) is connected to the feed port of the second heavy removal tower (18).

9. The purification method for ultra-high purity methanol according to claim 8, characterized in that, the top discharge of the second light removal tower (15) and the bottom discharge of the second heavy removal tower (18) are mixed and then returned to the first light removal tower (2).

10. The purification method for ultra-high purity methanol according to claim 8, characterized in that, the number of theoretical plates of the second light removal tower (15) and the second heavy removal tower (18) is 10 - 50, the top temperature is 60 - 70 °C, and the reflux ratio is 1 - 15.

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