Purification process for preparing semiconductor-grade high-purity methanol

Abstract

The invention provides a purification process for preparing semiconductor-grade high-purity methanol. According to the process, light impurities are preliminarily removed through rectification separation, particles and ions are deeply intercepted through a reverse osmosis membrane, ultra-trace impurities are finally removed through a pervaporation membrane, and multi-dimensional and high-precision collaborative purification is achieved. According to the invention, through innovative coupling of processes, multi-stage rectification and complex adsorption regeneration are avoided, and the content of metal ions, particulate matters and organic matters of a final product is ensured to fully meet or even be superior to those of SEMI G5-grade wet electronic chemicals. The whole process flow is compact, the energy consumption is low, and the adopted special membrane material has excellent long-term stability in a methanol system. The technology of each unit of the process is mature, the operation condition is mild, stable control and large-scale amplification are easy to realize, and an efficient and reliable ultra-pure methanol preparation scheme is provided for manufacturing semiconductors and high-end electronic chemicals.

Description

Technical Field

[0001] This invention belongs to the field of wet electronic chemical purification technology, specifically relating to a purification process for preparing semiconductor-grade high-purity methanol. This process utilizes an innovative multi-stage coupling of distillation separation with solvent-resistant reverse osmosis membranes and pervaporation membranes to systematically remove low-boiling-point organic matter, trace metal ions, submicron particles, and volatile organic impurities from methanol. The key indicators of the obtained methanol product, including metal ion content, particle number, and specific organic residues, fully meet and exceed the highest level (G5) technical standards in semiconductor manufacturing processes. It is suitable for critical processes such as cleaning, photolithography, and thin-film deposition in high-end electronic manufacturing fields such as integrated circuits, flat panel displays, and photovoltaic cells. Background Technology

[0002] Methanol, a key organic solvent in electronic chemical systems, is widely used in precision processes such as wafer cleaning, photoresist dilution, post-etching treatment, and the synthesis of specialty electronic chemicals in semiconductor manufacturing. As semiconductor technology nodes continue to shrink and the feature sizes of integrated circuits continue to decrease, the purity requirements for the chemicals used in manufacturing processes are becoming increasingly stringent. Trace amounts of moisture, metal ions, submicron and even nanoscale particles remaining in methanol, as well as organic byproducts such as aldehydes, ketones, and esters, can all become potential sources of contamination. These impurities can disrupt the uniformity of photoresists, affect the chemical stability of etching solutions, and may induce defects on the wafer surface, leading to device electrical performance degradation, reduced reliability, and a decrease in overall production yield.

[0003] Currently, the typical purity of industrial-grade anhydrous methanol is over 99.5%, but it still generally contains various organic impurities, metal ions at the ppm to ppb level, trace amounts of moisture, and insoluble particles, which is far from meeting the ultrapure requirements of wet electronic chemicals in semiconductor manufacturing. To improve methanol purity, existing technologies mainly focus on distillation, adsorption, membrane separation, and their combinations. However, these methods still have significant shortcomings in achieving comprehensive and deep purification and meeting the requirements for stable industrial production.

[0004] (1) Purification methods mainly based on distillation Distillation is currently the most widely used method for methanol purification, primarily used to remove low- or high-boiling-point organic impurities and some moisture. For example, Chinese patents CN200910069254.8, CN201210159304.3, CN202011164875.7, CN101570467B, CN102701906A, and CN112159305A all utilize oxidation-reduction reactions combined with single-stage or multi-stage distillation to increase methanol purity to 99.8%–99.9% or higher. However, this type of method focuses on removing moisture and conventional organic impurities, with weak capabilities for removing ultra-trace metal ions and submicron-sized particles. The purity of the products typically only reaches reagent-grade or chromatographic-grade standards, falling far short of the ppb or even ppt-level metal ion control and stringent particle counting standards required for semiconductor-grade methanol.

[0005] In addition, some patents employ extractive distillation (such as CN109678667A, CN10745817A, CN103304390A, CN103304371A, CN103319309A, etc.) to break the azeotropic system by introducing a third-component extractant. While this type of method can stably separate specific azeotropes, it generally faces problems such as complex process flow, difficulty in extractant recovery, and the risk of introducing secondary pollution. Furthermore, it does not systematically solve the problem of deep removal of metal ions and particulate impurities.

[0006] (2) Distillation-Adsorption Combined Process To deeply remove specific impurities, some technical solutions combine distillation with adsorption (e.g., CN201210421324.3, CN100384798C). This combined process can effectively reduce moisture and some ion content, but the adsorption capacity of the adsorbent is limited, requiring frequent regeneration or replacement, making operation cumbersome and costly. More importantly, its ability to retain solid particles and ultra-trace metal ions below the ppb level is insufficient, resulting in final products typically only reaching semiconductor G3 or G4 level, failing to meet the requirements for G5 grade ultra-high purity chemicals.

[0007] (3) Membrane separation and membrane combination processes Membrane separation technology, due to its high efficiency and energy saving, has been explored for methanol purification in recent years. Related patents (such as CN202311601207.X and CN11470958A) attempt to combine microfiltration, nanofiltration, or ion exchange membranes with distillation units to remove particles and some ions. The process described in CN11470958A can produce methanol with a purity of 99.99%, with some indicators meeting the SEMI C12 standard. However, existing membrane combination processes typically suffer from lengthy processes, numerous unit operations, and high overall energy consumption and equipment investment. More importantly, conventional reverse osmosis (RO) and nanofiltration (NF) membranes generally face technical bottlenecks such as membrane material swelling, poor chemical stability, rapid flux decline, and limited retention of monovalent metal ions when operating in strong organic solvents like methanol for extended periods. Meanwhile, pervaporation (PV) membranes are mainly used for dehydration or organic matter separation, with almost no retention effect on ions and particles. Although there are patents (such as CN202310659240.1) that attempt to combine PV and RO for the preparation of electronic-grade dimethyl carbonate (DMC), the products have not yet reached the highest level of SEMI G5, and the series connection of multiple membrane units may introduce new contamination risks during long-term operation, posing challenges to process stability and reliability.

[0008] In summary, existing methanol purification technologies generally have the following limitations: (1) Single purification dimension: It is difficult to remove moisture, multiple metal ions, submicron particles and complex organic impurities simultaneously and deeply in the same process.

[0009] (2) Purity ceiling limitation: Insufficient ability to remove ultra-trace (ppb / ppt level) metal ions and particles of specific sizes, the purity of the products mostly stays at the G3 / G4 level.

[0010] (3) Poor material tolerance: Existing membrane materials suffer from swelling and aging problems when operating in organic solvents such as methanol for a long time, resulting in unstable separation performance and short lifespan.

[0011] (4) Poor process economy: It relies heavily on multi-stage distillation or complex adsorption regeneration, with long process, high energy consumption, low yield, and great difficulty in industrial scale-up and stable operation.

[0012] Therefore, there is an urgent need in this field to develop a novel integrated process that is highly efficient and compact, with core separation materials possessing excellent methanol tolerance and long-term stability, and capable of synergistically achieving multi-dimensional deep purification. This process aims to overcome the purity bottlenecks and stability limitations of existing technologies, directly elevating industrial-grade methanol to ultra-high purity levels that meet the G5 grade requirements for semiconductors in a stable and economical manner, thereby providing a reliable raw material guarantee for high-end electronics manufacturing. This invention is proposed based on this objective. Summary of the Invention

[0013] To address the problems of existing methanol purification processes, such as complex processes, high energy consumption, limited impurity removal dimensions, difficulty in simultaneously removing trace metal ions, submicron particles, and specific organic impurities, and difficulty in stably preparing methanol that meets semiconductor G5 grade requirements, the present invention aims to provide a semiconductor-grade methanol preparation process that is compact, low in energy consumption, and can synergistically remove multiple types of impurities, so as to achieve efficient and stable conversion of industrial-grade anhydrous methanol to semiconductor-grade high-purity methanol.

[0014] The objective of this invention can be achieved through the following technical solutions: To achieve the above-mentioned objectives, this invention proposes a novel "distillation-membrane-membrane" integrated coupling process for preparing semiconductor-grade methanol, which includes the following sequential steps: (1) Distillation separation steps Industrial-grade anhydrous methanol is fed into a distillation column, where it is distilled and separated under controlled conditions of top temperature, bottom temperature, and reflux ratio to remove low-boiling-point impurities and light components, including one or more of dimethyl ether and formaldehyde, thereby obtaining a distillation product with an increased methanol mass fraction.

[0015] (2) Reverse osmosis membrane separation step The distillation product obtained in step (1) is fed into the reverse osmosis membrane separation unit in liquid form, and methanol is selectively permeated through the reverse osmosis membrane under pressure. The reverse osmosis membrane is made of solvent-resistant highly cross-linked material, which has an extremely low swelling rate (volume swelling rate ≤5%) and excellent long-term stability (720-hour continuous operation flux recovery rate ≥95%, rejection rate decay ≤2%). It can efficiently and stably retain suspended particles, colloids, metal ions and macromolecular organic impurities in the system to obtain a methanol system purified by reverse osmosis membrane.

[0016] (3) Deep purification step via pervaporation membrane The methanol system obtained in step (2) is fed into a pervaporation membrane separation unit. Under vacuum conditions on the permeate side, methanol selectively permeates through the pervaporation membrane as the preferred permeate component, while metal ions, submicron particles, and non-volatile organic impurities are enriched on the non-permeate side. The pervaporation membrane is modified for solvent stability, and its flux decay rate is less than 5% under long-term operation (≥1000 hours), thereby ensuring a continuous and stable supply of high-purity methanol that meets the requirements for semiconductor-grade applications.

[0017] Furthermore, in step (1), the mass fraction of industrial-grade anhydrous methanol is 99.1–99.9 wt.%, and the mass fraction of water is less than 0.01 wt.%; the total mass fraction of one or more of low-carbon alcohols, organic carbonyl compounds, ester compounds, or inorganic salts in the methanol-based mixture is 0.001–0.08 wt.%; the methanol-based mixture is in a liquid phase state before entering the reverse osmosis membrane separation unit.

[0018] Furthermore, in step (1), the theoretical plate number of the distillation column is 15 to 100; the reflux ratio of the distillation column is 2 to 8; the operating pressure at the top of the distillation column is 0.05 to 0.3 MPa; the operating temperature at the bottom of the distillation column is 70 to 120 ℃; and the mass fraction of methanol in the distillate at the top of the distillation column is 99.5 to 99.9 wt%.

[0019] Furthermore, the reverse osmosis membrane in step (2) comprises a support layer and a dense separation layer, wherein the dense separation layer is formed of highly cross-linked aromatic polyamide, polyimide, polybenzimidazole, or a modified material thereof; after continuous immersion in methanol for no less than 720 h, the methanol flux retention rate of the reverse osmosis membrane is no less than 90%; the reverse osmosis membrane is permeable to methanol at an operating pressure of 1–4 MPa, while retaining water and / or the impurities at a rate of 80–99.9%; the equivalent molecular weight cutoff range of the reverse osmosis membrane is 50–300 Da; the volume swelling rate of the reverse osmosis membrane in the methanol system is no higher than 10%; the reverse osmosis membrane uses at least three or more stages in series. Furthermore, in step (3), the methanol system separated by the reverse osmosis membrane further enters the pervaporation membrane separation unit, wherein the pervaporation membrane is a methanol selective pervaporation membrane, and methanol permeates through the pervaporation membrane as the preferred permeation component, and the permeation side product is collected as the final product.

[0020] Furthermore, the material of the selective layer of the pervaporation membrane in step (3) is selected from one or more of silicone rubber, fluorosilicone rubber, polydimethylsiloxane or its modified materials; the support layer is a high-purity non-leaching fluoroplastic such as pure polytetrafluoroethylene or polyvinylidene fluoride.

[0021] Furthermore, in step (3), the thickness of the selective layer of the pervaporation membrane is 1–50 μm, and the thickness of the support layer is 60–120 μm; the operating temperature is 10–50 ℃, and the system vacuum is 10–5000 Pa. The permeation side pipeline is an inert metal pipeline or a perfluoroalkoxyalkane pipeline, and adopts a flared structure or a beaded structure.

[0022] Beneficial effects: Compared with the prior art, the present invention has at least the following beneficial effects: 1. High purity and multi-dimensional precision purification By leveraging the complementary advantages and synergistic enhancement of three separation mechanisms—distillation, reverse osmosis membranes, and pervaporation—a systematic approach is taken to remove various contaminants, including low-boiling-point organic impurities, metal ions, submicron-sized particles, and volatile organic impurities. The final product fully meets and exceeds the stringent standards of G5-grade wet electronic chemicals for semiconductor manufacturing in terms of metal ion content, particle number, and key organic impurity indicators, achieving a high purification precision that is difficult to attain with a single technology.

[0023] 2. Excellent resistance to organic solvents and long-term stability Reverse osmosis membranes and pervaporation membranes specifically selected or designed for methanol systems exhibit low swelling ratio, high flux retention rate, and high selectivity. They can operate stably in methanol for a long time, avoiding the problem of rapid performance degradation of conventional membrane materials in organic solvents, thus ensuring product quality stability and process continuity. Attached Figure Description

[0024] Figure 1 This is a flowchart of a novel "distillation-membrane-membrane" integrated coupling process for preparing semiconductor-grade methanol, as described in an embodiment of the present invention. 1 represents a distillation column; 2 represents a three-stage series reverse osmosis membrane module; and 3 represents a pervaporation membrane. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0026] Example 1 A novel integrated "distillation-membrane-membrane" process for preparing semiconductor-grade methanol.

[0027] Using industrial-grade anhydrous methanol as raw material, the methanol mass fraction is 99.5 wt.% and the water content is 80 ppm. The raw material contains low-boiling-point impurities such as dimethyl ether and formaldehyde, as well as trace metal ions and submicron particles.

[0028] First, the aforementioned industrial-grade anhydrous methanol is continuously fed into a distillation column for distillation separation. The distillation column has 40 theoretical plates, a reflux ratio of 4, an operating pressure at the top of the column of 0.15 MPa, and an operating temperature at the bottom of the column of 85 °C. Low-boiling-point impurities are removed by distillation to obtain the overhead distillate, which contains 99.8 wt.% methanol.

[0029] Subsequently, the distilled methanol was fed into a reverse osmosis membrane separation unit in liquid form. The reverse osmosis membrane was a highly cross-linked aromatic polyamide composite membrane, operating at 25 °C and 2.5 MPa. Testing showed that the volume swelling rate of this reverse osmosis membrane in methanol was only 3.5%; after continuous immersion in methanol and operation for 720 h, its methanol flux recovery rate was 96%, and the rejection rate for labeled metal ions decreased by 1%, demonstrating excellent solvent resistance. During the separation process, methanol selectively permeated through the membrane layer, and suspended particles, colloids, metal ions, and large molecular organic impurities in the system were effectively retained, resulting in a methanol system purified by the reverse osmosis membrane.

[0030] Finally, the methanol purified by the reverse osmosis membrane is fed into a pervaporation membrane separation unit. The selective layer of the pervaporation membrane is polydimethylsiloxane (PDMS) with a thickness of 1 μm, and the support layer is polytetrafluoroethylene (PTFE). Operating at 30 °C and a permeate-side vacuum of 500 Pa, methanol selectively permeates through the pervaporation membrane as the preferred permeate component. Metal ions, submicron particles, and non-volatile organic impurities accumulate on the non-permeate side, and the condensate on the permeate side is collected as the final product. After 1000 hours of continuous operation testing, the methanol permeate flux decay rate of this pervaporation membrane is only 2%. Testing showed that the content of any single metal ion in the resulting methanol product is less than 10 ppt, and the number of particles larger than 0.2 μm is below the specified threshold. Simultaneously, the water content in the permeate-side methanol product is further reduced from approximately 70 ppm after reverse osmosis membrane separation to 34 ppm, stably meeting the technical requirement of semiconductor-grade methanol for a water content of less than 50 ppm, conforming to the G5 level wet electronic chemical standard.

[0031] Example 2 Integrated purification processes under different reverse osmosis membranes and operating conditions. Based on Example 1, the reverse osmosis membrane material and operating conditions were changed.

[0032] The industrial-grade anhydrous methanol used had a mass fraction of 99.5 wt.% and a water content of 80 ppm. The distillation steps were the same as in Example 1, but the reflux ratio was adjusted to 6, the overhead operating pressure was 0.1 MPa, and the methanol mass fraction in the resulting overhead distillate was 99.9 wt.%.

[0033] The distilled methanol is fed into a reverse osmosis membrane separation unit. The dense separation layer of the reverse osmosis membrane is made of polyimide. The unit operates at 30 °C and 3.0 MPa, employing a three-stage series membrane module structure. This polyimide membrane undergoes a special cross-linking treatment, and its volume swelling rate in the methanol system is measured to be 2.8%. After 720 hours of continuous operation, no significant decrease in rejection rate was observed.

[0034] Subsequently, the methanol treated by the reverse osmosis membrane enters the pervaporation membrane separation unit. The selective layer of the pervaporation membrane is made of fluorosilicone rubber material with a thickness of 20 μm. The operating temperature is 40 ℃, the vacuum degree on the permeate side is 1000 Pa, and the flux decay is 2.1% during continuous operation.

[0035] Testing revealed that the content of any single metal ion in the obtained methanol product was less than 7 ppt, and the key volatile organic impurities were below the detection limit. After separation by a pervaporation membrane, the water content in the methanol product decreased from approximately 70 ppm after the distillation-reverse osmosis step to 30 ppm, indicating that the pervaporation membrane has a significant synergistic removal effect on trace moisture in this process.

[0036] Example 3 Semiconductor-grade methanol was prepared under continuous operation conditions using the same process route as in Example 2, but the process parameters were optimized for continuous operation.

[0037] The industrial-grade anhydrous methanol has a mass fraction of 99.8 wt.% and a water content of 50 ppm. The distillation column has a theoretical plate number of 60, a reflux ratio of 3, an operating pressure at the top of the column of 0.2 MPa, and a bottom temperature of 90 ℃.

[0038] The reverse osmosis membrane is a polybenzimidazole modified composite membrane. It operates continuously for 1000 hours at an operating pressure of 1.8 MPa, during which the methanol flux retention rate is not less than 90%. After 1000 hours of operation, the methanol flux recovery rate of the reverse osmosis membrane is 94%, and the metal ion rejection rate decreases by 0.3%.

[0039] The pervaporation membrane employs a PDMS / fluoroplastic composite structure with a selective layer thickness of 2 μm, an operating temperature of 25 ℃, and a permeate-side vacuum of 200 Pa. During 1000 h of continuous operation, the water content of the methanol product permeated through the pervaporation membrane remained consistently at 28 ppm without significant fluctuations, indicating that the described integrated "distillation-membrane-membrane" process demonstrates excellent control over trace moisture in methanol under long-term operating conditions.

[0040] Comparative Example 1 The methanol purification method using only the distillation-reverse osmosis membrane combination uses the same industrial-grade anhydrous methanol as in Example 1 as the raw material, and only uses the distillation and reverse osmosis membrane separation steps, without setting up a pervaporation membrane separation unit.

[0041] After distillation and reverse osmosis membrane treatment, the low-boiling-point organic impurities in the obtained methanol were significantly reduced and the particle content was improved. However, some volatile organic impurities were still detected. The metal ion content in the product remained stable below 81 ppt, and the water content was still 163 ppm. It was difficult to consistently meet the requirement of semiconductor-grade methanol for water content below 50 ppm, and it could not consistently meet the requirements of semiconductor G5 grade.

[0042] Comparative Example 2 The methanol purification method using only the distillation-pervaporation membrane combination uses the same industrial-grade anhydrous methanol as in Example 1 as the raw material. After the distillation step, the methanol directly enters the pervaporation membrane separation unit without a reverse osmosis membrane separation step.

[0043] Although the pervaporation membrane has a certain removal effect on moisture, metal ions and particles, the metal ion content in the methanol product is still significantly excessive because it does not pass through the reverse osmosis membrane for pre-retention of ions and particles. The water content can only be reduced to about 71 ppm. The overall quality cannot meet the G5 grade requirements, and the product quality can only reach the G4 grade, which is difficult to meet the methanol purity requirements of advanced semiconductor manufacturing.

[0044] Testing items unit raw material Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 water ppm 912 34 30 28 163 71 Particles larger than 0.2 µm cells / mL 816 1 2 1 19 3 Lithium (Li) ppb 0.001 ND ND ND ND ND Beryllium (Be) ppb 0.001 ND ND ND ND ND Sodium (Na) ppb 0.526 0.009 0.007 0.005 0.081 0.031 Magnesium (Mg) ppb 0.063 0.002 0.001 0.001 0.013 0.010 Aluminum (Al) ppb 0.010 0.003 0.002 0.001 0.007 0.004 Potassium (K) ppb 0.027 0.007 0.003 0.001 0.009 0.005 Calcium (Ca) ppb 0.028 0.005 0.001 ND 0.005 0.002 Titanium (Ti) ppb 0.003 ND ND ND ND ND Vanadium (V) ppb 0.016 0.002 ND ND 0.008 0.001 Chromium (Cr) ppb 0.036 0.002 0.001 ND 0.002 0.001 Manganese (Mn) ppb 0.004 ND ND ND ND ND Iron (Fe) ppb 0.008 0.001 ND ND 0.004 0.001 Cobalt (Co) ppb 0.002 ND ND ND ND ND Nickel (Ni) ppb 0.002 0.001 ND ND 0.001 0.001 Copper (Cu) ppb 0.002 0.001 ND ND 0.002 0.001 Zinc (Zn) ppb 0.007 ND ND ND 0.002 0.001 Gallium (Ga) ppb 0.006 ND ND ND 0.001 ND Germanium (Ge) ppb 0.001 ND ND ND ND ND Arsenic (As) ppb 0.001 ND ND ND ND ND Strontium (Sr) ppb 0.002 ND ND ND 0.001 ND Zirconium (Zr) ppb 0.002 0.001 0.001 ND 0.001 0.001 Niobium (Nb) ppb 0.003 ND ND 0.001 0.002 0.001 Molybdenum (Mo) ppb 0.004 ND 0.001 ND 0.002 0.001 Silver (Ag) ppb 0.006 ND 0.001 ND 0.004 0.002 Cadmium (Cd) ppb 0.004 ND ND ND ND ND Tin (Sn) ppb 0.003 ND ND ND ND ND Antimony (Sb) ppb 0.002 ND ND ND ND ND Barium (Ba) ppb 0.003 ND ND ND ND ND Thallium (Tl) ppb 0.002 ND ND ND ND ND Lead (Pb) ppb 0.001 ND ND ND ND ND

Claims

1. A purification process for the production of semiconductor grade high purity methanol, characterized in that, The process comprises the following sequentially connected process units: (1) distillation column separation unit An industrial grade anhydrous methanol raw material is input into a distillation column for distillation separation. Under the conditions of a set overhead pressure, a set column bottom temperature and a set reflux ratio, low boiling point impurities and light components are removed, and metal ions are preliminarily separated, to obtain a primary purified methanol fraction; (2) reverse osmosis membrane separation unit The primary purified methanol fraction obtained in step (1) is subjected to a reverse osmosis membrane assembly under pressurized conditions, to remove suspended particles, colloids, metal ions and macromolecular organic impurities contained therein; (3) pervaporation membrane separation The methanol obtained in step (2) is transported to a pervaporation membrane separation system. Under the condition of maintaining a vacuum on the membrane permeation side, ultra-trace level metal ions, sub-micron particles and residual volatile organic compounds in the methanol are deeply removed, to finally obtain a semiconductor grade high purity methanol product.

2. The purification process of claim 1, wherein: In the industrial grade anhydrous methanol raw material, the mass fraction of methanol is 99.1-99.9 wt.%, and the mass fraction of water is less than 0.01 wt.%; the impurities contained include one or more of low carbon alcohols, organic carbonyl compounds, ester compounds or inorganic salts, and the total mass fraction of the impurities is 0.001-0.08 wt.%.

3. The process of claim 1, wherein: In step (1), the theoretical plate number of the distillation column is 15-100 stages; the operating reflux ratio is 2-8; the operating pressure at the top of the column is 0.05-0.3 MPa; the operating temperature at the bottom of the column is 70-120℃; and the mass fraction of methanol in the methanol fraction produced from the top of the column is 99.5-99.9 wt.%.

4. The purification process of claim 1, wherein: In step (2), the reverse osmosis membrane comprises a support layer and a dense separation layer, and the material of the dense separation layer is high crosslinking aromatic polyamide, polyimide, polybenzimidazole or modified materials thereof; the reverse osmosis membrane has excellent methanol solvent resistance and long-term operation stability, and the volume swelling rate thereof in a methanol system is not higher than 5%; after continuous immersion or operation in methanol for 720 hours, the methanol flux recovery rate thereof is not lower than 90%, and the decrease in the rejection rate of impurities is not more than 2%; the rejection rate of water and / or the impurities thereof is 80-99.9% under an operating pressure of 1-4 MPa; the equivalent molecular weight rejection range thereof is 50-300 Da; the volume swelling rate thereof in a methanol system is not higher than 10%; and the reverse osmosis membrane separation unit is operated in a manner of at least three membrane assemblies connected in series.

5. The purification process of claim 1, wherein: In step (3), the pervaporation membrane is a methanol preferential permeation membrane, and methanol as a preferential permeation component permeates through the pervaporation membrane and is collected on the membrane permeation side as a final high purity product.

6. The purification process of claim 1, wherein: In step (3), the selective layer material of the pervaporation membrane is selected from one or more of silicone rubber, fluorosilicone rubber, polydimethylsiloxane or modified materials thereof; and the material of the support layer thereof is pure polytetrafluoroethylene or polyvinylidene fluoride.

7. The purification process of claim 6, wherein: The selective layer of the pervaporation membrane has a thickness of 1-50 μm, and the support layer has a thickness of 60-120 μm; the operating temperature of the pervaporation membrane separation unit is 10-50 ℃, and the system vacuum degree of the membrane permeation measurement is 10-5000 Pa; the pervaporation membrane has long-term stability in a methanol system, and after continuous operation for 1000 hours, the attenuation rate of the separation factor is less than 5%, and the attenuation rate of the methanol permeation flux is less than 10%; the collection pipeline on the permeation side is made of inert metal material or perfluoroalkoxy alkane material, and adopts a flared or bead-in type interface structure.

8. A process for the preparation of semiconductor grade high purity methanol, characterized in that, The semiconductor and high-purity methanol product is prepared by the purification process in any one of claims 1-7; the metal ion content of the semiconductor and high-purity methanol product meets the SEMI G5 standard, the water content is ≤50 ppm, and the total number of submicron particles is lower than the corresponding specification threshold.

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