Preparation method of ultra-clean high-purity methanol for semiconductor electronics

Abstract

The invention discloses a preparation method of ultra-clean high-purity methanol for semiconductor electronics, which comprises the following steps: (1) mixing industrial methanol with a metal chelate, stirring for 1 hour at 20-35 DEG C, and dehydrating for 1-1.5 hours by using a 4A molecular sieve; (2) enabling the dehydrated methanol solution to pass through an adsorption device filled with 200kg of metal boron adsorbent, and reacting for 2-2.5 hours at the temperature of 40-50 DEG C; (3) carrying out ion exchange to remove anions and cations; (4) carrying out double-tower rectification on the methanol solution treated in the step (3) through a pressurizing tower and an atmospheric tower in sequence; and (5) conveying the rectified methanol solution to a hundred-grade purification room by a pump, and carrying out precision filtration. The content of methanol is increased to 99.9% or above, the content of anions is reduced to 100 ppb or below, the content of cations is reduced to 0.1 ppb or below, the water content is reduced to 200 ppm or below, the content of particles larger than 0.2 micrometer is reduced to 200 / ml or below, and the overall index reaches the G4 standard.

Description

Technical Field

[0001] The invention relates to the technical field of chemical purification, and in particular to a method for preparing ultra-clean high-purity methanol for semiconductor electronics. Background Art

[0002] Contamination on the chip surface will lead to a decrease in the yield of integrated circuits (ICs). In order to obtain high-quality and high-yield integrated circuit chips, these contaminants must be removed. Ultra-clean high-purity methanol is one of the key basic chemical materials in the production process of semiconductors and integrated circuits, and is mainly used for chip cleaning. The purity and cleanliness of methanol have a very important impact on the yield, electrical performance and reliability of integrated circuits.

[0003] With the rapid development of semiconductor and integrated circuit technology industries, IC oxide films are becoming thinner and thinner. Excessive anion content in high-purity reagents will dissolve into the oxide film, seriously affecting the conductive effect; excessive cation content in high-purity reagents will lead to unstable voltage, even electrochemical corrosion of products, and a significant decrease in product yield; excessive particle content in high-purity reagents will cause leakage and even short circuit. Therefore, with the continuous improvement of the integration of integrated circuits, the control of soluble impurities, anion content, cation content and solid particles in ultra-clean high-purity reagents is becoming more and more stringent. G4-level methanol is required for cleaning 12-inch chips, with a purity higher than 99.9%, anions not higher than 100ppb, cations not higher than 100ppt, moisture not higher than 200ppm, and particles larger than 0.2 microns not higher than 200 / ml. At present, there is no domestic enterprise producing G4-level ultra-clean high-purity methanol, and market demand can only be solved by imports.

[0004] Therefore, there is an urgent need to develop a method for preparing ultra-clean high-purity methanol for semiconductor electronics. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing ultra-clean high-purity methanol for semiconductor electronics. The general content of industrial methanol is 99.5%, and the impurities mainly include organic substances such as alcohols, aldehydes, ketones, ethers, esters, alkanes, and three major categories such as ions and water. The present invention mainly uses molecular sieve dehydration, metal boron adsorption, ion exchange, double-tower distillation and precision filtration to increase the methanol content to more than 99.9%, anions are reduced to less than 100 ppb, cations are reduced to less than 0.1 ppb, moisture is reduced to less than 200 ppm, and particles larger than 0.2 microns are reduced to less than 200 / ml. The overall index reaches the G4 standard and import substitution is achieved.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing ultra-clean high-purity methanol for semiconductor electronics comprises the following steps:

[0008] (1) Molecular sieve dehydration:

[0009] Mixing industrial grade methanol and metal chelate, stirring at 20-35°C for 1 hour, and dehydrating through 4A molecular sieve for 1-1.5 hours; the amount of metal chelate added is 0.05-0.08% of the weight of industrial grade methanol;

[0010] (2) Metal boron adsorption:

[0011] The methanol solution after dehydration in step (1) is passed through an adsorption device containing 200 kg of metal boron adsorbent at a temperature of 40-50° C. and a reaction time of 2-2.5 h;

[0012] (3) Ion exchange to remove anions and cations:

[0013] Passing the methanol solution treated in step (2) through an anion and cation exchange treatment tank to remove anions and cations;

[0014] (4) Distillation:

[0015] The methanol solution treated in step (3) is sequentially distilled through a pressure tower and a normal pressure tower;

[0016] (5) Precision filtration:

[0017] The methanol solution after distillation in step (4) is pumped to a Class 100 clean room for precision filtration to obtain a finished product.

[0018] Preferably, the metal chelate is one or a combination of diethylenetriamine, pentaacetamidotrimethylenephosphonic acid, and aminotriacetic acid.

[0019] Preferably, the metal chelate is diethylenetriamine and pentaacetamidotrimethylenephosphonic acid in a mass ratio of 2:2.5, or aminotriacetic acid and pentaacetamidotrimethylenephosphonic acid in a mass ratio of 3:2.

[0020] Preferably, the molecular sieve is used in an amount of 300 kg.

[0021] Preferably, the metal boron adsorbent is prepared by the following steps:

[0022] (1) 5.5 wt% aluminum hydroxide, 2.7 wt% meglumine, 1.8 wt% carboxymethyl chitosan and 90 wt% pure water were mixed uniformly, and the mixture was recorded as mixture A;

[0023] (2) Adding mixture A to a polyvinyl alcohol aqueous solution, adding an emulsifier after stirring for 40 minutes, continuing to stir for 30 minutes, pouring into a mold, and curing at 60° C. for 4-5 hours to obtain a metal boron adsorbent; wherein the mass ratio of mixture A, polyvinyl alcohol aqueous solution and emulsifier is 6:3.5:0.5; and the content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 25wt%.

[0024] Preferably, the anion and cation exchange treatment tank contains a strong alkaline anion resin and a strong acidic cation resin, wherein the strong alkaline anion resin is Lanxess MonoPlus MP 800, DuPont AmberLite TM HPR550, Kramar CG-400-Ⅱ or a combination thereof; the strong acid cationic resin is Dow MARATHON C, DuPont Rohm and Haas HPR1200NA, Lanxess S1567 or a combination thereof.

[0025] Preferably, the column length of the anion and cation exchange treatment tank is 2.5 meters, the diameter is 0.2 meters, and the volume ratio of the strong basic anion resin to the strong acidic cation resin is 1:1.3.

[0026] Preferably, the double-tower distillation is specifically:

[0027] (1) The methanol solution treated in step (3) is pumped to a pressure tower for distillation, and the top of the pressure tower adopts two-stage condensation, the feed temperature is 45-55°C, the temperature of the top of the pressure tower is 110-120°C, the top operating pressure is 550-600Kpa, the reflux ratio is 2-4, and the bottom temperature is 110-150°C;

[0028] (2) The methanol solution coming out from the bottom of the pressure tower is pumped to the atmospheric tower for further distillation. The top temperature of the atmospheric tower is 65°C, the top pressure is 10-20Kpa, and the reflux ratio is 2-4.

[0029] This process uses two-stage condensation at the top of the tower, which can reduce the loss of methanol in distillation and improve heat utilization.

[0030] Preferably, the Class 100 cleanroom adopts a four-stage filtration mode, the filter element is a Pall filter element ABFG1UCFRL3EH1K3, the filter element precisions are 0.5μm, 0.2μm, 0.1μm, 0.05μm respectively, and the filtration pressure is 0.6-0.8Mpa.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention adopts molecular sieve dehydration, which has low cost and obvious effect, and the molecular sieve can be regenerated and reused.

[0033] The present invention mixes industrial-grade methanol with metal chelates during molecular sieve dehydration, thereby preventing methanol from being oxidized to formaldehyde. The essence of oxidation reaction is a series of chemical reactions produced by the interaction between oxygen molecules in oxygen and metal ions in other substances. The addition of metal chelates can reduce the presence of free metal ions, thereby reducing the incidence of oxidation reaction.

[0034] The present invention adopts a metal boron adsorbent to efficiently adsorb boron ions, reducing the boron ions from the raw material ppm level to below 100ppt.

[0035] The present invention utilizes ion exchange to efficiently remove anions and cations.

[0036] The ethanol content in the final methanol of the traditional single-tower distillation is about 500ppm. The present invention uses a pressure tower and a normal pressure tower in combination, and adopts a double-tower distillation technology. The load of the main distillation tower can be reduced by 30%, steam can be saved by 20%, cooling water can be saved by 15%, the ethanol content can be as low as 10ppm, and the overall purity of methanol can reach 99.97%.

[0037] The present invention adopts four-stage filtration, and the filtration efficiency is increased by 25% compared with the three-stage filtration, and the yield of the product is increased by 20%.

[0038] The present invention adopts a Class 100 clean room and a fully automatic packaging system, which increases the efficiency by 30% compared with traditional manual packaging and avoids pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a process flow chart of the present invention;

[0040] Among them, 1-raw material tank, 2-valve, 3-molecular sieve tank, 4-adsorption device, 5-anion and cation exchange treatment tank, 6-pressure distillation tower, 7-atmospheric distillation tower, 8-hundred-level purification room, 9-finished product. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with examples, but it should be noted that the examples do not limit the scope of protection claimed for the present invention.

[0042] A method for preparing ultra-clean high-purity methanol for semiconductor electronics comprises the following steps:

[0043] (1) Molecular sieve dehydration:

[0044] Industrial grade methanol (99.5%) is used as raw material, enters into raw material tank 1 filled with metal chelate and mixes with metal chelate, after stirring at 20-35°C for 1 hour, it is introduced into molecular sieve tank 3 filled with 4A molecular sieve for dehydration, the dehydration time is 1-1.5 hours, and the water content of methanol is reduced from the original 500-600ppm to below 100ppm.

[0045] The amount of the metal chelate added is 0.05-0.08% of the weight of industrial-grade methanol. The metal chelate is one or a combination of diethylenetriamine, pentaacetic acid aminotrimethylene phosphoric acid, and aminotriacetic acid. Preferably, the metal chelate is diethylenetriamine and pentaacetic acid aminotrimethylene phosphoric acid in a mass ratio of 2:2.5, or aminotriacetic acid and pentaacetic acid aminotrimethylene phosphoric acid in a mass ratio of 3:2. The amount of the molecular sieve is 300kg.

[0046] (2) Metal boron adsorption:

[0047] The content of metallic boron in industrial-grade methanol is extremely high, generally at the ppm level. Metal complexing agents have little complexing effect on boron, and it is difficult to reach the 100ppt level using ion exchange treatment alone. The present invention uses an independently developed metallic boron adsorbent that can effectively adsorb boron ions, and the boron ions after treatment are as low as 100ppt.

[0048] Specifically, the methanol solution after dehydration in step (1) is passed through an adsorption device 4 containing 200 kg of metal boron adsorbent at a temperature of 40-50° C. and a reaction time of 2-2.5 hours. Controlling the reaction temperature and reaction time within the above range effectively improves the adsorption performance of the metal boron adsorbent.

[0049] The metal boron adsorbent is prepared by the following steps:

[0050] (1) 5.5 wt% aluminum hydroxide, 2.7 wt% meglumine, 1.8 wt% carboxymethyl chitosan and 90 wt% pure water were mixed uniformly, and the mixture was recorded as mixture A;

[0051] (2) Adding mixture A to a polyvinyl alcohol aqueous solution, adding an emulsifier after stirring for 40 minutes, continuing to stir for 30 minutes, pouring into a mold, and curing at 60° C. for 4-5 hours to obtain a metal boron adsorbent; wherein the mass ratio of mixture A, polyvinyl alcohol aqueous solution and emulsifier is 6:3.5:0.5; and the content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 25wt%.

[0052] (3) Ion exchange:

[0053] The methanol solution after the treatment in step (2) is passed through an anion and cation exchange treatment tank 5 to remove anions and cations. The anion and cation exchange treatment tank 5 contains a strong alkaline anion resin and a strong acidic cation resin. The strong alkaline anion resin is Lanxess MonoPlus MP 800, DuPont AmberLite TM The strong acid cationic resin is one or a combination of Dow MARATHON C, DuPont Rohm and Haas HPR1200NA, and Lanxess S1567.

[0054] The column length of the anion and cation exchange treatment tank is preferably 2.5 meters, and the diameter is preferably 0.2 meters. The volume ratio of the strong basic anion resin to the strong acidic cation resin is preferably 1:1.3.

[0055] (4) Distillation:

[0056] The methanol solution treated in step (3) is sequentially passed through a pressure tower 6 and a normal pressure tower 7 for double-tower distillation.

[0057] The double-tower distillation has two main distillation towers. Compared with the traditional single-tower distillation, under the same process conditions, the double-tower distillation technology can reduce the load of the main distillation tower by 30%, save 20% of steam, and save 15% of cooling water. At the same time, the ethanol content in the final methanol of the traditional single-tower distillation is about 500ppm, while the double-tower distillation can reduce the ethanol content to 10ppm, and the overall purity of methanol can reach 99.97%. In the pressurized tower, organic matter with a boiling point lower than the boiling point of methanol, such as dimethyl ether and methyl formate, is removed from the top of the tower. In the atmospheric pressure tower, organic matter with a boiling point higher than the boiling point of methanol, such as ethanol and propanol, is removed from the bottom.

[0058] Double tower distillation is specifically:

[0059] (1) The methanol solution treated in step (3) is pumped to a pressure tower for rectification. The top of the pressure tower adopts two-stage condensation, most of which is re-condensed in the first condenser of the pre-tower, and a small part is further condensed in the second condenser, and then sent back to the top of the tower by a reflux pump as reflux liquid. The feed temperature is 45-55°C, the temperature of the top of the pressure tower is 110-120°C, the operating pressure of the top of the tower is 550-600Kpa, the reflux ratio is 2-4, and the bottom temperature is 110-150°C.

[0060] (2) The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric tower for further distillation. The temperature at the top of the atmospheric tower is 65°C, the pressure at the top is 10-20Kpa, and the reflux ratio is 2-4. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is pumped back to the top of the atmospheric tower as reflux liquid by the atmospheric tower reflux pump, and another part of it is directly pumped to the Class 100 clean room 8 for filtration after passing the test.

[0061] After ion exchange and double-tower distillation, the methanol content in methanol increased to 99.9%, the anion content decreased to 100 ppb, and the cation content decreased to 0.1 ppb.

[0062] (5) Precision filtration:

[0063] The methanol solution after distillation in step (4) is pumped to a Class 100 clean room 8 for precision filtration to obtain a finished product 9. The Class 100 clean room adopts a four-stage filtration mode, the filter element is made of perfluorinated material, the brand is Pall filter element ABFG1UCFRL3EH1K3, the filter element precision is 0.5μm, 0.2μm, 0.1μm, 0.05μm, and the filtration pressure is 0.6-0.8Mpa. After filtration, the particles larger than 0.2 microns are less than 200 / ml, and are transported to the automatic filling station through a dust-free pipeline. The machine is fully automatic for filling to avoid pollution.

[0064] In order to illustrate the advantages of the present invention, the following is described by comparing Examples 1-2 with Comparative Examples 1-2:

[0065] Example 1

[0066] Mix 0.2kg of diethylenetriamine and 0.25kg of pentaacetic acid aminotrimethylenephosphoric acid evenly, add to the raw material tank, add 800kg of industrial grade methanol 99.5%, stir for 1h at 25℃, pass into the molecular sieve tank filled with 300kg 4A molecular sieve for dehydration, the dehydration time is 1.2 hours. After dehydration, it is transported into the adsorption device filled with 200kg of metal boron adsorbent, the temperature is 40℃, and the reaction time is 2h. Then it enters the anion and cation exchange treatment tank, the cation is DuPont AmberLite TM HPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower for distillation, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged.

[0067] Example 2

[0068] Mix 0.3kg of aminotriacetic acid and 0.2kg of pentaacetic acid aminotrimethylenephosphoric acid evenly, add to the raw material tank, add 800kg of industrial grade methanol 99.5%, stir for 1h at 35℃, pass into the molecular sieve tank filled with 300kg 4A molecular sieve for dehydration, the dehydration time is 1.5 hours. After dehydration, it is transported to the adsorption device filled with 200kg of metal boron adsorbent, the temperature is 45℃, and the reaction time is 2.2h. Then it enters the anion and cation exchange treatment tank, the cation is Lanxess MonoPlusMP 800, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower, the feed temperature is 50℃, the temperature of the top of the pressure tower is 110℃, the top operating pressure is 600Kpa, the reflux ratio is 3.0, and the bottom temperature is 120℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 15Kpa, and the reflux ratio is 3.0. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.7Mpa. After the particle test is qualified, the finished product is packaged.

[0069] Example 3

[0070] Mix 0.2kg of diethylenetriamine and 0.25kg of pentaacetic acid aminotrimethylenephosphoric acid evenly, add to the raw material tank, add 800kg of industrial grade methanol 99.5%, stir for 1h at 25℃, pass into the molecular sieve tank filled with 300kg 4A molecular sieve for dehydration, the dehydration time is 1.2 hours. After dehydration, it is transported into the adsorption device filled with 200kg of metal boron adsorbent, the temperature is 45℃, and the reaction time is 2.5h. Then it enters the anion and cation exchange treatment tank, the cation is DuPont AmberLite TMHPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower for distillation, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged.

[0071] Comparative Example 1 (No Molecular Sieve Dehydration)

[0072] 0.2kg diethylenetriamine and 0.25kg pentaacetic acid aminotrimethylenephosphoric acid were mixed evenly, added to the raw material tank, and 800kg industrial grade methanol 99.5% was added. Stirred for 1h at 25℃, and transported to the adsorption device with 200kg metal boron adsorbent, the temperature was 40℃, and the reaction time was 2h. Then it entered the anion and cation exchange treatment tank, and the cation was DuPont AmberLite TM HPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The three-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, and 0.1μm respectively. The filtration pressure is 0.8Mpa. After filtration, the finished product is packaged.

[0073] Comparative Example 2 (no metal boron adsorbent adsorption)

[0074] 0.2 kg of diethylenetriamine and 0.25 kg of pentaacetic acid aminotrimethylenephosphoric acid were mixed evenly, added to the raw material tank, and 800 kg of industrial grade methanol was added. Stirred for 1 hour at 25 ° C, and passed into the molecular sieve tank filled with 300 kg of 4A molecular sieve for dehydration. The dehydration time was 1.2 hours. Then it entered the anion and cation exchange treatment tank, and the cation was DuPont AmberLite TM HPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the atmospheric tower with a top temperature of 65℃, a top pressure of 12Kpa, and a reflux ratio of 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is pumped back to the top of the atmospheric tower as reflux liquid by the atmospheric tower reflux pump, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, the filter element is made of perfluorinated material, the brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged.

[0075] Comparative Example 3 (without metal chelate)

[0076] Add 800kg of industrial grade methanol 99.5% into the raw material tank, and pass it into the molecular sieve tank with 300kg of 4A molecular sieve for dehydration. The dehydration time is 1.2 hours. After dehydration, it is transported into the adsorption device with 200kg of metal boron adsorbent, the temperature is 40℃, and the reaction time is 2h. Then it enters the anion and cation exchange treatment tank, and the cation is DuPont AmberLite TM HPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower for distillation, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the Class 100 clean room for precision filtration after passing the test. The four-stage filtration mode is adopted. The filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3. The filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged and compared in column 4

[0077] Mix 0.2kg of diethylenetriamine and 0.25kg of pentaacetic acid aminotrimethylenephosphoric acid evenly, add to the raw material tank, add 800kg of industrial grade methanol 99.5%, stir for 1h at 25℃, pass into the molecular sieve tank filled with 300kg 4A molecular sieve for dehydration, the dehydration time is 1.2 hours. After dehydration, it is transported into the adsorption device filled with 200kg of metal boron adsorbent, the temperature is 35℃, and the reaction time is 2h. Then it enters the anion and cation exchange treatment tank, the cation is DuPont AmberLite TM HPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower for distillation, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged.

[0078] Comparative Example 5

[0079] Mix 0.2kg of diethylenetriamine and 0.25kg of pentaacetic acid aminotrimethylenephosphoric acid evenly, add to the raw material tank, add 800kg of industrial grade methanol 99.5%, stir for 1h at 25℃, pass into the molecular sieve tank filled with 300kg 4A molecular sieve for dehydration, the dehydration time is 1.2 hours. After dehydration, it is transported into the adsorption device filled with 200kg of metal boron adsorbent, the temperature is 40℃, and the reaction time is 1.5h. Then it enters the anion and cation exchange treatment tank, the cation is DuPont AmberLite TMHPR550, anion is LANXESS S1567, the volume ratio of the two is 1:1.3. Then it is pumped to the pressure tower for distillation, the feed temperature is 45℃, the temperature of the top of the pressure tower is 115℃, the top operating pressure is 550Kpa, the reflux ratio is 2.5, and the bottom temperature is 125℃. The methanol solution coming out of the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric tower is 65℃, the top pressure is 12Kpa, and the reflux ratio is 2.5. The methanol vapor coming out of the atmospheric tower is condensed in the atmospheric tower condenser and then discharged to the atmospheric reflux tank. A part of it is sent back to the top of the atmospheric tower by the atmospheric tower reflux pump as reflux liquid, and another part of it is pumped to the 100-level clean room for precision filtration after passing the test. The four-stage filtration mode is adopted, and the filter element is made of perfluorinated material. The brand is Pall filter element ABFG1UCFRL3EH1K3, and the filter element precision is 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively. The filtration pressure is 0.8Mpa. After the particle test is qualified, the finished product is packaged.

[0080] Analysis method of ultra-high purity methanol produced in Examples 1-3 and Comparative Examples 1-5: content was analyzed by Shimadzu GC2014, anions were analyzed by Swiss Metrohm 930 ion chromatograph molecular analysis, cations were analyzed by Thermo Fisher ICAP RQ inductively coupled plasma mass spectrometer, water content was analyzed by Mettler C20S Karl Fischer titrator, and particles were analyzed by Japanese Rion KS-42BF liquid particle counter.

[0081] The analysis results are shown in the following table:

[0082]

[0083]

[0084]

[0085] It can be seen from the results in Table 1 that the ultra-high purity methanol products obtained by the methods of Examples 1-3 of the present invention have a methanol content of more than 99.9%, and a single anion is less than 100 ppb, a single cation is less than 0.1 ppb, a moisture content is less than 200 ppm, and particles larger than 0.2 microns are less than 200 / ml, which meets the G4 standard.

[0086] Compared with Example 1, Comparative Example 2 did not use a metal boron adsorbent, and the boron content of the product was 670.1 ppb (much greater than 0.056 ppb in Example 1), and the ethanol content of the product was 509.62 ppm (much greater than 10.15 ppm in Example 1).

[0087] The metal chelate is added in the present invention mainly to prevent methanol from being oxidized to formaldehyde. The essence of the oxidation reaction is a series of chemical reactions produced by the interaction between oxygen molecules in oxygen and metal ions in other substances. The addition of the metal chelate can reduce the presence of free metal ions, thereby reducing the incidence of the oxidation reaction. Compared with Example 1, the formaldehyde content of Comparative Example 3 without the metal chelator is significantly increased to 392.7ppm (much greater than 8.94ppm in Example 1).

[0088] When using a metal boron adsorbent to adsorb metal boron in industrial-grade methanol, when the adsorption temperature or adsorption time is not appropriate, the adsorption effect is not ideal. In Comparative Example 4, the adsorption temperature is 35°C, the adsorption reaction time is 2h, the adsorption temperature is lower than 40-50°C, and the boron content after adsorption is 20.2ppb (much greater than 0.056ppb in Example 1). In Comparative Example 5, the adsorption temperature is 40°C, the adsorption reaction time is 1.5h, the adsorption time is lower than 2-2.5h, and the boron content after adsorption is 18.5ppb (much greater than 0.056ppb in Example 1).

[0089] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing ultra-clean high-purity methanol for semiconductor electronics, characterized in that: The following steps are involved: (1) Molecular sieve dehydration: Mixing industrial grade methanol and metal chelate, stirring at 20-35°C for 1 hour, and dehydrating through 4A molecular sieve for 1-1.5 hours; the amount of metal chelate added is 0.05-0.08% of the weight of industrial grade methanol; (2) Metal boron adsorption: The methanol solution after dehydration in step (1) is passed through an adsorption device containing 200 kg of metal boron adsorbent at a temperature of 40-50° C. and a reaction time of 2-2.5 h; (3) Ion exchange to remove anions and cations: Passing the methanol solution treated in step (2) through an anion and cation exchange treatment tank to remove anions and cations; (4) Distillation: The methanol solution treated in step (3) is sequentially distilled through a pressure tower and a normal pressure tower; (5) Precision filtration: The methanol solution after distillation in step (4) is pumped to a Class 100 clean room for precision filtration to obtain a finished product.

2. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The metal chelate is one or a combination of diethylenetriamine, pentaacetamidotrimethylenephosphonic acid, and aminotriacetic acid.

3. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The metal chelate is diethylenetriamine and pentaacetamidotrimethylenephosphonic acid in a mass ratio of 2:2.5, or aminotriacetic acid and pentaacetamidotrimethylenephosphonic acid in a mass ratio of 3:

2.

4. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The molecular sieve is used in an amount of 300 kg.

5. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The metal boron adsorbent is prepared by the following steps: (1) 5.5 wt% aluminum hydroxide, 2.7 wt% meglumine, 1.8 wt% carboxymethyl chitosan and 90 wt% pure water were mixed uniformly, and the mixture was recorded as mixture A; (2) Adding mixture A to a polyvinyl alcohol aqueous solution, adding an emulsifier after stirring for 40 minutes, continuing to stir for 30 minutes, pouring into a mold, and curing at 60° C. for 4-5 hours to obtain a metal boron adsorbent; wherein the mass ratio of mixture A, polyvinyl alcohol aqueous solution and emulsifier is 6:3.5:0.5; and the content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 25wt%.

6. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The anion and cation exchange treatment tank contains a strong alkaline anion resin and a strong acidic cation resin, wherein the strong alkaline anion resin is Lanxess MonoPlus MP 800, DuPont AmberLite TM HPR550, Kramar CG-400-Ⅱ or a combination thereof; the strong acid cationic resin is Dow MARATHON C, DuPont Rohm and Haas HPR1200NA, Lanxess S1567 or a combination thereof.

7. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 6, characterized in that: The column length of the anion and cation exchange treatment tank is 2.5 meters and the diameter is 0.2 meters.

8. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 6, characterized in that: The volume ratio of the strong basic anion resin to the strong acidic cation resin is 1:1.

3.

9. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The double tower distillation is specifically as follows: (1) The methanol solution treated in step (3) is pumped to a pressure tower for distillation, and the top of the pressure tower adopts two-stage condensation, the feed temperature is 45-55°C, the temperature of the top of the pressure tower is 110-120°C, the top operating pressure is 550-600Kpa, the reflux ratio is 2-4, and the bottom temperature is 110-150°C; (2) The methanol solution coming out from the bottom of the pressure tower is pumped to the atmospheric pressure tower for further distillation. The top temperature of the atmospheric pressure tower is 65°C, the top pressure is 10-20Kpa, and the reflux ratio is 2-4.

10. The method for preparing ultra-clean high-purity methanol for semiconductor electronics according to claim 1, characterized in that: The Class 100 cleanroom adopts a four-stage filtration mode, and the filter element is Pall filter element ABFG1UCFRL3EH1K3. The filter element precisions are 0.5μm, 0.2μm, 0.1μm, and 0.05μm respectively, and the filtration pressure is 0.6-0.8Mpa.

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