Method for producing purified isopropanol

Abstract

The present invention provides a method for producing purified isopropanol from crude isopropanol containing butyl formate as an impurity, the method comprising a pressure distillation step in which the crude isopropanol is subjected to pressure distillation.

Description

Technical Field

[0001] This invention relates to a method for producing purified isopropanol from crude isopropanol containing butyl formate as an impurity. Background Technology

[0002] Isopropanol (hereinafter also referred to as "IPA") possesses the properties of dissolving both water and organic solvents, and is widely used as a solvent for coatings, inks, and various synthetic raw materials. Furthermore, high-purity IPA is extensively used in the rinsing section of semiconductor substrates in semiconductor manufacturing equipment, and its usage is expected to increase in the future. Distillation purification is a known method for purifying crude IPA used in the production of high-purity IPA. (See Non-Patent Literature 1) High-purity IPA is expensive to manufacture, and its use in the rinsing section of semiconductor substrates can sometimes contribute to increased manufacturing costs. Furthermore, the IPA waste liquid recovered after use in the semiconductor substrate rinsing section is typically incinerated, but this releases carbon dioxide, a contributor to global warming. Therefore, from an environmental protection perspective, it is desirable to reduce the amount of IPA waste liquid being disposed of. Consequently, the demand for purifying and reusing IPA waste liquid is constantly increasing (see, for example, Patent Document 1).

[0003] However, the rinsing section of the semiconductor substrate is generally located adjacent to the rear section of the cleaning section. The cleaning solution used in the cleaning section is typically ultrapure water or a high-aqueous solution. Therefore, in the rinsing section, the water adhering to the surface of the semiconductor substrate is removed. Consequently, the IPA waste liquid recovered from the rinsing section is a low-aqueous solution. Furthermore, IPA is also widely used in the developing and pre-wetting sections of semiconductor manufacturing equipment. In addition, water is mostly used in semiconductor manufacturing equipment for various purposes. Therefore, IPA-containing waste liquid is discharged from the semiconductor manufacturing equipment equipped with the rinsing section for semiconductor substrates. For example, in Patent Document 2, the water content of the IPA-containing waste liquid is set to approximately 5% by mass. As a method for recovering IPA from such IPA-containing waste liquid, Patent Document 3 proposes a method for distilling and purifying IPA-containing waste liquid with a water content of 5-15%.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2017-144410 Patent Document 2: Japanese Patent Application Publication No. 2014-55120 Patent Document 3: Chinese Patent Publication No. 112999679 Non-patent literature Non-patent literature 1: Organic Synthetic Chemistry, Vol. 35, No. 9, 1977, pp. 762-766 Summary of the Invention

[0005] The problem that the invention aims to solve On the other hand, in semiconductor manufacturing equipment, various compounds other than IPA are used in the cleaning and rinsing sections. Examples of these compounds include, for instance, the solvent components of photoresist materials used in the developing section and the solvent components of adhesives used for various purposes. Therefore, the IPA waste liquid discharged from the semiconductor manufacturing equipment after passing through the cleaning and rinsing sections contains these solvent components in addition to water.

[0006] The inventors of this application conducted research on the production of high-purity IPA capable of purifying IPA waste liquid for use in semiconductor manufacturing equipment, and determined that butyl formate is present as a solvent component that is difficult to remove from IPA waste liquid. Therefore, the object of this invention is to provide a method for producing purified IPA from crude IPA containing butyl formate as an impurity.

[0007] Methods for solving problems In view of the above-mentioned problems, the inventors of this application conducted research on the separation and removal of butyl formate based on the distillation purification of crude IPA, and found that it is difficult to produce purified IPA. Specifically, when crude IPA contains butyl formate and no water, an azeotropic mixture of butyl formate and IPA is obtained, so even distillation under non-pressurized conditions is difficult to separate and remove butyl formate. On the other hand, when crude IPA contains water and butyl formate, butyl formate can be separated and removed as a low-boiling impurity if distilled under non-pressurized conditions. However, to obtain an azeotropic mixture of IPA and water, azeotropic distillation is required, making the production of purified IPA complicated. Furthermore, it was found that when crude IPA also contains formic acid and 1-butanol, butyl formate is regenerated by dehydrating the crude IPA.

[0008] Based on the above insights, a method for producing purified IPA containing butyl formate and without water was studied. The results showed that by pressurizing the crude IPA, purified IPA with a high degree of butyl formate removal could be obtained from the top of the distillation column as distillate, thus completing the present invention.

[0009] That is, one aspect of the present invention is a method for producing purified isopropanol, which is a method for producing purified isopropanol from crude isopropanol containing butyl formate as an impurity. The aforementioned method includes a pressure distillation step of pressure distilling the aforementioned crude isopropanol. In the above-described aspect of the present invention, the following method is preferred.

[0010] (1) The ratio of butyl formate to isopropanol in the crude isopropanol is more than 10 ppb by mass and less than 100,000 ppb by mass.

[0011] (2) The crude isopropanol was subjected to pressure distillation under an absolute pressure of 120 kPa or more and 1000 kPa or less.

[0012] (3) It also includes a dehydration step of dehydrating the crude isopropanol stock solution containing formate ions, 1-butanol and water to obtain the aforementioned crude isopropanol.

[0013] (4) The ratio of formate ions in the crude isopropanol stock solution to isopropanol is more than 10 ppb by mass and less than 100,000 ppb by mass.

[0014] (5) The ratio of 1-butanol to isopropanol in the aforementioned crude isopropanol stock solution is more than 10 ppb by mass and less than 100,000 ppb by mass.

[0015] (6) The aforementioned crude isopropanol stock solution is waste liquid recovered from semiconductor manufacturing equipment.

[0016] Invention Effects According to the present invention, highly purified IPA can be produced from crude IPA containing butyl formate as an impurity. Therefore, IPA waste liquid recovered from semiconductor manufacturing apparatuses with rinsing sections for semiconductor substrates can be easily regenerated into high-purity IPA, and the high-purity IPA can be used as a semiconductor solution, especially as a rinsing solution for semiconductor substrates, which has great industrial value. Attached Figure Description

[0017] Figure 1A An overall graph showing the mole fraction of liquid phase IPA versus gas phase IPA at each pressure.

[0018] Figure 1B An enlarged graph showing the range of high mole fractions of liquid phase IPA versus gas phase IPA at each pressure.

[0019] Figure 2 A schematic diagram of the low-boiling distillation column used in Example 6 is shown. Detailed Implementation

[0020] The method for producing purified IPA in this embodiment is a method for producing purified IPA from crude IPA containing butyl formate as an impurity. The aforementioned method includes a pressure distillation step of pressure distillation of the crude IPA. While the details of why the method for producing purified IPA in this embodiment can remove a high degree of butyl formate from crude IPA containing butyl formate as an impurity are not clear, the inventors of this application speculate as follows: As mentioned above, IPA waste liquid discharged from semiconductor manufacturing equipment sometimes contains water and butyl formate. In this case, if distillation is performed under non-pressure conditions, butyl formate can be separated and removed. On the other hand, when the IPA waste liquid does not contain water, even if distillation is performed under non-pressure conditions, butyl formate cannot be separated and removed because it becomes an azeotropic mixture of butyl formate and IPA. Furthermore, if the temperature is above the boiling point of IPA, particularly above 100°C, the saturated vapor pressure difference between IPA and butyl formate becomes large, making it difficult for them to form an azeotropic mixture. Therefore, it is speculated that if distillation is carried out under pressure, it will not become an azeotropic mixture of butyl formate and IPA, and butyl formate can be separated and removed.

[0021] In this specification, unless otherwise specified, the expressions "A~B" regarding numerical values ​​A and B mean "above A and below B". When only the unit is indicated for numerical value B in such expressions, that unit also applies to numerical value A. In the following description, unless otherwise specified, including the examples, the terms "ppm", "ppb", and "ppt" indicating concentration are based on mass. The method for manufacturing purified IPA according to this embodiment will be described in detail below.

[0022] <Crude IPA> In the method for producing purified IPA according to this embodiment, crude IPA containing butyl formate as an impurity is subjected to pressure distillation. Butyl formate has a boiling point of approximately 106°C at atmospheric pressure. The crude IPA is not particularly limited and can be a reaction product obtained by reacting propylene with water via the propylene process, a reaction product obtained by reducing acetone, or even IPA waste liquid.

[0023] The ratio of butyl formate to isopropanol in crude IPA is not particularly limited, but is preferably 10 to 100,000 ppb, more preferably 100 to 10,000 ppb. When the ratio of butyl formate to isopropanol in crude IPA is within the above range, the separation and removal effect of butyl formate in this embodiment can be significantly achieved. On the other hand, even if the ratio of butyl formate to isopropanol in crude IPA exceeds 100,000 ppb, butyl formate can be removed by adjusting the pressure distillation conditions described below.

[0024] The crude IPA may also contain other components (such as water, acetone, 1-propanol). At this time, if the content of IPA in the crude IPA is low, multiple steps are required to produce purified IPA, so there is a tendency for low efficiency and a decrease in the separation and removal efficiency of butyl formate. Therefore, the content of IPA in the crude IPA is preferably 95% or more, more preferably 99% or more. When the content of IPA in the crude IPA is low, it is preferably supplied to the method for producing purified IPA of the present embodiment after removing impurities by a known method. The content of IPA in the crude IPA can be measured by gas chromatography.

[0025] In addition, the crude IPA may also contain water. However, when the crude IPA contains a large amount of water, there is a tendency for the separation and removal efficiency of butyl formate to decrease. Therefore, the method for producing purified IPA of the present embodiment may also include a dehydration step of dehydrating the crude IPA stock solution containing water to obtain crude IPA. Therefore, the content of water in the crude IPA is preferably 1000 ppm or less, more preferably 100 ppm or less, and further preferably 1 - 50 ppm. As a method for dehydrating the crude IPA stock solution containing water, for example, distillation, adsorption, membrane permeation, etc. can be cited. The content of water in the crude IPA can be measured by the Karl Fischer method.

[0026] <Preparation method of crude IPA> The crude IPA stock solution is not particularly limited. Hereinafter, the preparation method of crude IPA when using IPA waste liquid as the crude IPA stock solution will be described in detail. It should be noted that as the crude IPA stock solution, a liquid obtained by diluting the IPA waste liquid with water can be used.

[0027] <IPA waste liquid> IPA waste liquid is often discharged from various industrial equipment such as the manufacture and use of paints and inks, and these recovered liquids can all be applied without limitation, but the most suitable is the waste liquid recovered from a semiconductor manufacturing apparatus having a rinsing section for a semiconductor substrate. In particular, the waste liquid recovered from the rinsing section of the semiconductor substrate is likely to have a composition suitable for manufacturing purified IPA and can be suitably applied. In addition, the IPA waste liquid may also contain a developer, a pre-wetting liquid, an etching liquid, a cleaning liquid, a stripping liquid, a drying liquid, etc. discharged from the semiconductor manufacturing apparatus.

[0028] 6]The content of IPA in the IPA waste liquid is preferably 5% by mass or more and 95% by mass or less, more preferably 10 - 80% by mass, and particularly preferably 15 - 30% by mass. On the other hand, the content of water in the IPA waste liquid is preferably less than 95% by mass, more preferably 20 - 90% by mass, and particularly preferably 70 - 85% by mass. When the content of water in the IPA waste liquid is high, there is a tendency for the equipment to become large and the transportation cost to increase.

[0029] IPA waste liquid sometimes contains formate ions, butyl formate and 1-butanol. The total amount of formate ions, butyl formate and 1-butanol in the IPA waste liquid is preferably in the range of 100 - 1000000 ppb relative to IPA, and more preferably in the range of 1000 - 100000 ppm relative to IPA. When the total amount of formate ions, butyl formate and 1-butanol in the IPA waste liquid is in the above range relative to IPA, the separation and removal effect of butyl formate can be significantly exerted. As the reasons for the mixing of butyl formate and 1-butanol, for example, it is considered that: butyl formate and 1-butanol are used in the previous step of the semiconductor cleaning step; they are mixed as impurities such as butyl acetate. In addition, as the reason for the mixing of formate ions, for example, it is considered that: formate ions are used in the previous step of the semiconductor cleaning step; they are mixed as impurities of acetic acid and methanol. In addition, for IPA waste liquid, the mixing of air is usually not managed, and formic acid may sometimes be generated due to oxygen in the air. It is known that if IPA comes into contact with air, formic acid will be generated, especially if water is present, it is easy to generate formic acid.

[0030] IPA waste liquid may also contain: olefins such as butene, pentene, hexene; alkanes such as butane, pentane, hexane; aldehydes such as formaldehyde, acetaldehyde, acrolein; ketones such as acetone, butanone; alcohols such as methanol, ethanol, 2-methyl-2-propanol; chlorinated alkanes such as dichloromethane, chloroform, carbon tetrachloride, vinyl chloride; silylated alcohols such as trimethylsilylated IPA, trimethylsilylated ethanol and other low-boiling impurities with boiling points lower than IPA. The total amount of low-boiling impurities in the IPA waste liquid is preferably in the range of 0.1 - 10000 ppm relative to IPA, and more preferably in the range of 1 - 100 ppm relative to IPA.

[0031] In addition, IPA waste liquid may also contain high-boiling impurities with boiling points higher than IPA. Specifically, when it is the waste liquid of semiconductor chemical liquids, especially the waste liquid of cleaning liquids and drying liquids, IPA waste liquid mostly also contains: metals such as iron, chromium, nickel, copper, zinc, sodium, potassium, calcium, magnesium; carboxylic acids such as formic acid, acetic acid, propionic acid; salts with anions such as nitrate ions, nitrite ions, sulfate ions, chloride ions, fluoride ions; aldehyde-ketones such as crotonaldehyde, 2-pentanone; alcohols such as 1-propanol, 2-butanol, 1-butanol; ethers such as 1-methoxy-2-propanol, 1-(2-methoxypropoxy)propan-2-ol, 1-(2-methoxy-2-methylethoxy)-2-propanol; aromatics such as toluene, xylene (ortho, meta, para); alkanes such as octane, decane, hexadecane; carboxylic acid esters such as isopropyl acetate, isopropyl propionate; phthalate esters such as dioctyl phthalate, dibutyl phthalate; adipate esters such as dioctyl adipate and other high-boiling impurities.

[0032] <IPA Waste Liquid Dehydration Method> When the IPA waste liquid contains a large amount of water, it is preferable to dehydrate the IPA waste liquid. Specifically, the IPA waste liquid is distilled, and after a distillate containing an azeotropic mixture of IPA and water is drawn out from the top of the high-boiling distillation column, the distillate is subjected to azeotropic distillation, and a bottom liquid containing IPA is drawn out to obtain crude IPA. At this time, a part of the low-boiling impurities and high-boiling impurities can also be separated and removed.

[0033] <Method for removing low-boiling impurities and high-boiling impurities in IPA waste liquid> When the IPA waste liquid contains low-boiling impurities and high-boiling impurities, preferably, the IPA waste liquid is distilled to draw out a first bottom liquid containing IPA and water, and then the second bottom liquid containing IPA obtained by removing the water in the first bottom liquid as described above is distilled to obtain crude IPA in the form of a bottom liquid. By subjecting the crude IPA to pressure distillation, the impurities can be highly removed.

[0034] At this time, sometimes the ratio of butyl formate in the second bottom liquid to IPA is greater than the ratio of butyl formate in the first bottom liquid to IPA. It is speculated that this is because butyl formate is generated during the removal of water in the first bottom liquid. That is, it is speculated that when the IPA waste liquid contains formate ions and 1-butanol, the formate ions and 1-butanol undergo dehydration condensation to form butyl formate. From the viewpoint of尽可能地降低纯化IPA中的甲酸丁酯相对于IPA而言的比例, the ratio of butyl formate in the IPA waste liquid to IPA is preferably 10 to 100000 ppb, more preferably 100 to 10000 ppb. The ratio of 1-butanol in the IPA waste liquid to IPA is preferably 10 to 100000 ppb, more preferably 100 to 10000 ppb.

[0035] The ratio of formate ions in the IPA waste liquid to IPA can be measured by ion chromatography. The ratios of butyl formate and 1-butanol in the IPA waste liquid to IPA can be measured by GC / MS.

[0036] Crude IPA can be prepared by the above method.

[0037] <Pressure distillation of crude IPA> In the method for manufacturing purified IPA according to the present embodiment, the crude IPA is subjected to pressure distillation. Specifically, the crude IPA is distilled under a pressure condition where the absolute pressure is above atmospheric pressure. Since the boiling point of butyl formate is higher than that of IPA, if there is no azeotropy during distillation, it can be drawn out as a bottom liquid. Figure 1A and Figure 1BA graph showing the mole fractions of liquid-phase IPA (X-axis) and gas-phase IPA (Y-axis) at each pressure is provided. Here, when the mixture of IPA and butyl formate is distilled, the total mole fraction becomes 1 because the two-component system reaches vapor-liquid equilibrium. At a pressure (absolute pressure) of 101 kPa, if the mole fraction of IPA is 0.96 or higher, it coincides with the diagonal line (the line representing the mole fractions of liquid and gas-phase IPA) (see [link to graph]). Figure 1B This means that the concentrations of IPA and butyl formate are the same in both the liquid and gas phases. Therefore, if the pressure (absolute pressure) is 101 kPa, butyl formate and IPA will azeotropically combine, making it difficult to separate and remove butyl formate from the crude IPA.

[0038] On the other hand, when the pressure (absolute pressure) is 200 kPa and 300 kPa (see...) Figure 1B Butyl formate and IPA do not azeotropically combine, and during pressure distillation, butyl formate can be extracted as a bottom liquid. The absolute pressure during pressure distillation is preferably 120–1000 kPa, more preferably 150–800 kPa, and even more preferably 200–500 kPa. If the absolute pressure during pressure distillation is below 120 kPa, butyl formate cannot be sufficiently separated and removed; if it exceeds 1000 kPa, the equipment becomes expensive. The temperature during pressure distillation can be appropriately set according to the boiling point of IPA at the desired absolute pressure. For example, when the absolute pressure is 200 kPa, the boiling point of IPA is approximately 100°C.

[0039] The pressure distillation column can be either a plate column or a packed column, preferably a plate column. The theoretical number of plates in the pressure distillation column is preferably 10 to 200, more preferably 20 to 100. Examples of plates in a plate column include cross-flow plates and spray plates. Examples of packing materials in a packed column include Raschig rings and Luxing rings. Examples of materials used for the column and packing material include iron, stainless steel, Hastelloy, borosilicate glass, quartz glass, and fluoropolymers (e.g., polytetrafluoroethylene).

[0040] In a pressurized distillation column, the number of sections from the feed section to the bottom of the column, calculated using the theoretical plate count, is at least five, and the number of sections from the feed section to the top of the column, calculated using the theoretical plate count, is also at least five. Furthermore, the bottom and top of the column are not included in the theoretical plate count for the feed section. The overall theoretical plate count of the pressurized distillation column is preferably determined through actual operation and compositional analysis.

[0041] Preferably, a portion of the purified IPA distilled from the top of the pressurized distillation column is refluxed, and the remaining purified IPA is extracted as distillate. That is, the reflux ratio (reflux rate / distillate rate) is preferably 1.1 to 100, more preferably 1.2 to 10, and even more preferably 1.5 to 5. By adjusting the reflux ratio, theoretical plate number, and absolute pressure to minimize the amount of IPA extracted from the bottom of the column, butyl formate can be separated and removed, resulting in purified IPA with reduced butyl formate content as a high-boiling impurity. The ratio of butyl formate to IPA in the purified IPA is preferably 100 ppb or less, more preferably 10 ppb or less, and even more preferably 0.1 ppb or less.

[0042] In the pressure distillation step of the method for producing purified IPA in this embodiment, if there are other distillation steps, it is preferred to perform it as the last distillation step.

[0043] In the pressure distillation step of the method for producing purified IPA in this embodiment, high-boiling impurities with boiling points higher than IPA contained in crude IPA can be removed together with butyl formate. As for high-boiling impurities, there are no particular limitations as long as their boiling point is higher than that of IPA; examples include: metals such as iron, chromium, nickel, copper, zinc, sodium, potassium, calcium, and magnesium; carboxylic acids such as formic acid, acetic acid, and propionic acid; salts with anions such as nitrate ions, nitrite ions, sulfate ions, chloride ions, and fluoride ions; aldehydes and ketones with 4 to 8 carbon atoms such as 2-pentanone, 3-methyl-2-pentanone, 4-methyl-2-pentanone, butyraldehyde, 3-methylbutyraldehyde, and 3-methylpentanaldehyde; 1-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 2-methyl-3-pentanol, 3- Alcohols with 3 to 8 carbon atoms, such as methyl-3-pentanol, 1-methyl-2-pentanol, 1-heptanol, 2-methylhexanol, 1-octanol, and 2-methylheptanol; ethers such as 1-methoxy-2-propanol, 1-(2-methoxypropoxy)prop-2-ol, and 1-(2-methoxy-2-methylethoxy)-2-propanol; alkanes with 8 to 20 carbon atoms, such as octane, decane, and hexadecane; carboxylic acid esters such as isopropyl acetate, isopropyl propionate, isopropyl formate, and butyl formate; phthalate esters such as dioctyl phthalate and dibutyl phthalate; and adipate esters such as dioctyl adipate. The method for producing purified IPA according to this embodiment can remove high-boiling impurities to a high degree.

[0044] High-boiling impurities extracted from the bottom of the tower in this way can be discharged outside the system and the high concentration of impurities can be separated and used for other purposes, or reused as fuel, etc.

[0045] <Other Steps> The purified IPA can be further purified by adsorption or the like as needed. For example, the purified IPA can be filtered through a filter to remove metal particles, inorganic particles, organic particles, etc., or metal ions, etc. can be removed by an ion exchange resin or the like.

[0046] Examples Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples. In addition, in this example, unless otherwise stated, % and ppm are based on mass. In addition, the content of impurities in the sample is analyzed by the following method.

[0047] (Method for measuring the content of water in the sample) Instrument: Karl Fischer moisture meter CA-200 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) When it is expected that the water content in the sample exceeds 1%, the sample is diluted with IPA, and then the water content in the diluted sample is measured. The water content in the IPA used for dilution has been previously measured and confirmed to be 100 ppm or less. When it is expected that the water content in the sample is 1% or less, the water content in the sample can be measured without dilution. It should be noted that when the water content in the sample is more than expected, it only takes more time for the measurement and does not affect the measured value. In addition, when the water content in the sample is 100 ppm or less, it is preferable to collect more than 5 g of the sample in a glove box with a dew point of -60°C or lower using a Terumo syringe and measure the water content in the sample. This analytical method can perform quantification as long as the water content in the sample is 1 ppm or more.

[0048] (Method for measuring the ratio of butyl formate in the sample relative to IPA) <A: When the water content in the sample is 1% by mass or more> After setting the water content in the sample to 95% by mass, the ratio of butyl formate in the sample relative to IPA is analyzed by headspace gas chromatography-mass spectrometry (HS / GC / MS). In addition to this, this analytical method can also analyze 1-butanol, trimethylsilylated IPA, etc. with high sensitivity. In addition, the detection limit of this analytical method is 1 ppb for butyl formate, 1 ppb for 1-butanol, and 1 ppb for trimethylsilylated IPA. In addition, the SIM value can be arbitrarily set for each compound to be quantified.

[0049] -Measurement conditions- Apparatus: Gas chromatography-mass spectrometry apparatus (GC / MS) 8890, 5977B (manufactured by Agilent Technologies), headspace sampler 8697 (manufactured by Agilent Technologies) Injection mode: Splitless Carrier: Helium Chromatographic column: DB-1 (length 60 m, inner diameter 0.32 mm, thickness 5 μm) (manufactured by J&W Scientific) Column temperature: After maintaining at 30°C for 15 minutes, it was heated to 250°C at a rate of 20°C / minute and further maintained at 250°C for 10 minutes.

[0050] Column flow rate: 1.4 mL / minute Inlet pressure: 8.4 psi Inlet temperature: 200°C Injection volume: 1 mL (gas phase part of the vial in the headspace method) Ion source temperature: 230°C Quadrupole temperature: 150°C SIM (Selective Ion Monitoring): 56 (butyl formate, 1-butanol), 117 (trimethylsilylated IPA) Solvent heating temperature (headspace): 60°C Solvent heating time (headspace): 15 minutes <B: When the water content in the sample is less than 1% by mass> The ratio of butyl formate in the sample relative to IPA was determined by gas chromatography - mass spectrometry (GC / MS). It should be noted that in addition to this, this analytical method can also analyze 1-butanol, trimethylsilylated IPA, etc. with high sensitivity. In addition, the detection limit of this analytical method is 0.1 ppb for butyl formate, 0.1 ppb for 1-butanol, and 0.1 ppb for trimethylsilylated IPA.

[0051] It should be noted that the SIM values can be arbitrarily set for each compound to be quantified. Since butyl formate forms an azeotrope with IPA, it is difficult to further lower the detection limit by an enrichment method at atmospheric pressure. By performing enrichment under pressure as in the method for manufacturing purified IPA in this embodiment, or using an adsorbent such as activated carbon that easily adsorbs substances with low polarity, the detection limit can be further lowered to 1 ppt or less.

[0052] - Measurement conditions - Apparatus: Gas chromatography - mass spectrometer (GC / MS) 8890, 5977B (manufactured by Agilent Technologies) Injection mode: Splitless Carrier: Helium Chromatographic column: DB-1 (length 60 m, inner diameter 0.32 mm, thickness 5 μm) (manufactured by J&W Scientific) Column temperature: After maintaining at 30°C for 15 minutes, the temperature was increased to 250°C at a rate of 20°C / min, and then maintained at 250°C for 10 minutes.

[0053] Column flow rate: 1.4 mL / min Inlet pressure: 8.4 psi Inlet temperature: 200℃ Injection volume: 5 μL Ion source temperature: 230℃ Quadrupole temperature: 150℃ SIM (Selective Ion Detection): 56 (Butyl Formate, 1-Butanol), 117 (Trimethylsilylated IPA) (Method for determining the ratio of formate ions to IPA in a sample) Regarding the organic acid radicals and various anions contained in the sample, the organic acids were identified by concentrated ion chromatography according to the following measuring apparatus and conditions, and their proportion relative to IPA was evaluated.

[0054] Instrument Name: ICS2100 (Thermo Fisher Scientific) Anion Analyzer Detector: Conductivity detector Column: IonPacAS18 Flow rate: 1 mL / min Temperature conditions: 30℃ Gradient conditions: 2mM KOH → 15 minutes, 5mM KOH → 25 minutes, 40mM KOH → 40 minutes, 40mM KOH Concentrated chromatographic column: UTAC-LP2 Injection volume: 20 mL Detection limit: 10 ppt (formate ion, acetate ion, propionate ion, butyrate ion, isobutyrate ion, fluoride ion, chloride ion, bromide ion, iodide ion, nitrate ion, nitrite ion, sulfate ion) <Example 1> A 1-inch SUS tube was installed on an autoclave (manufactured by Nippon Pressure Glass Co., Ltd.), and a HELI PACK (manufactured by TO-TOKU ENGINEERING Co., Ltd.) made by SUS was placed in the SUS tube to a height of 50 cm. A pressure distillation column was set up with a structure that uses tap water to cool and reflux the top of the column, and allows the refluxed liquid to be extracted. 1000 g of crude IPA, adjusted to a ratio of butyl formate (manufactured by FUJIFILM WakoPure Chemical Co., Ltd.) to IPA of 10000 ppb, was placed in the autoclave, and then refluxed at atmospheric pressure for 30 minutes to extract the gas from the system. Next, the autoclave was sealed, and the temperature at the bottom of the column was set to 110°C for pressure distillation of the crude IPA. At this point, the absolute pressure at the bottom of the column at 110°C was approximately 280 kPa. In addition, approximately 10 g of purified IPA was extracted from the top of the column as distillate every 30 minutes, for a total extraction of 100 g. The ratio of butyl formate to IPA in the purified IPA was analyzed, and the result was 90 ppb. The theoretical number of plates in the pressure distillation column was estimated to be 12.

[0055] <Comparative Example 1> Except that the autoclave was not sealed and the temperature at the bottom of the column was set to 83°C, the crude IPA was subjected to pressure distillation in the same manner as in Example 1 to obtain purified IPA. The ratio of butyl formate to IPA in the purified IPA was analyzed, and the result was 10,000 ppb.

[0056] <Example 2> The pressure distillation process was simulated using the process simulation software AspenPlus (made by Aspen Technology).

[0057] Specifically, the bottom liquid is drawn from the bottom (a 2L container) of a pressure distillation column with 80 trays. A condenser is installed at the top of the pressure distillation column (the uppermost section of the column), so that a portion of the purified IPA condensed in the condenser is refluxed back to the top of the column, and the remaining purified IPA is drawn off as distillate.

[0058] Crude IPA containing 10,000 ppb of butyl formate as an impurity was fed at 10 L / h to a feed section 30 units below the top of the pressure distillation column for pressure distillation. The temperature at the top of the column was set to 93°C, and the absolute pressure at the top was set to 155 kPa. A reflux rate of 2.5 L / h and a reflux ratio of approximately 1.5 were used to extract distillate from the condenser at a rate of 40 mL / h. Furthermore, the bottom liquid was extracted from the bottom of the column at a rate of approximately 10 mL / h to maintain a volume of approximately 1.5 L at the bottom. The ratio of butyl formate to IPA in the purified IPA was analyzed and found to be 10 ppb.

[0059] <Example 3> Except that the temperature at the top of the column was set to 101°C and the absolute pressure at the top of the column was set to 200 kPa, pressure distillation simulation was performed in the same manner as in Example 2. The ratio of butyl formate to IPA in the purified IPA was analyzed, and the result was below 0.1 ppb.

[0060] <Example 4> Except for setting the temperature at the top of the column to 110°C and the absolute pressure at the top of the column to 275 kPa, pressure distillation simulation was performed in the same manner as in Example 2. The ratio of butyl formate to IPA in the purified IPA was analyzed, and the result was below 0.1 ppb.

[0061] <Example 5> Except that the temperature at the top of the column was set to 85°C and the absolute pressure at the top of the column was set to 110 kPa, pressure distillation simulation was performed in the same manner as in Example 2. The ratio of butyl formate to IPA in the purified IPA was analyzed, and the result was 1000 ppb.

[0062] <Example 6> IPA-containing aqueous waste liquid is recovered from a semiconductor manufacturing apparatus equipped with a semiconductor substrate rinsing unit, and three days' worth of recovered volume is stored in a waste liquid receiving tank. The IPA-containing aqueous waste liquid contains 80% water and 20% IPA, with impurities relative to IPA in the following proportions: butyl formate 100 ppb, formate ions 21,000 ppb, 1-butanol 5,000 ppb, and trimethylsilylated IPA 5,000 ppb. Water is supplied to the waste liquid receiving tank to achieve a water content of 90% and an IPA content of 10% relative to the IPA-containing aqueous waste liquid, yielding a water content adjustment solution as crude isopropanol stock solution.

[0063] As a low-boiling distillation column, it uses a container with 20 theoretical plates, a bottom 3 of 2L capacity, and a top condenser 2. Figure 2The low-boiling distillation column 1 shown is used to distill the water content adjustment liquid 4. The water content adjustment liquid 4 is supplied at a rate of 10 L / h and distilled to the top of the low-boiling distillation column 1. At this time, the temperature at the bottom of the column is set to 75–85°C, and the absolute pressure at the top of the column is set to 101 kPa. Furthermore, the reflux rate is set to 10 L / h, the reflux ratio is set to approximately 1000, and the distillate 5 is discharged from the condenser 2 at a rate of 10 mL / h and incinerated. In addition, to maintain the liquid volume at the bottom of the column 3 at approximately 1.5 L, a first bottom liquid containing IPA and water is drawn off at a rate of approximately 10 L / h as bottom liquid 6.

[0064] The ratio of butyl formate to IPA in the bottom liquid of the first batch was determined, and the result was below 1 ppb, which is below the detection limit, indicating that butyl formate has been removed by the low-boiling distillation column.

[0065] The same distillation column as the low-boiling distillation column 1 is used as the high-boiling distillation column to distill the first bottom liquid. Specifically, the first bottom liquid is fed to the feed section of the high-boiling distillation column and distilled, and an azeotropic mixture containing IPA and water (mass ratio of 87.5:12.5) is drawn from the top of the column.

[0066] The first distillate is fed to the feed section of the azeotropic distillation column for azeotropic distillation. Benzene is used as the azeotropic agent to separate the benzene distillate from the top of the column from the water, discharging the water and returning the benzene to the azeotropic distillation column. The second bottom liquid, containing less than 100 ppm of water and IPA, is drawn from the bottom of the column.

[0067] The ratio of butyl formate to IPA in the second batch bottom solution was determined, and the result was 1000 ppb. This is presumably because butyl formate was generated during the removal of water from the first batch bottom solution. Additionally, the ratio of trimethylsilylated IPA to IPA in the second batch bottom solution was determined, and the result was 2500 ppb.

[0068] Using the same distillation column as low-boiling distillation column 1, the second bottom liquid was distilled. Low-boiling impurities were extracted from the top of the column, and crude IPA, with the low-boiling impurities removed, was obtained from the bottom liquid. The ratio of butyl formate to IPA in the crude IPA was determined, and the result was 1000 ppb. The ratio of trimethylsilyl IPA to IPA in the crude IPA was determined, and the result was less than 1 ppb, below the detection limit.

[0069] Except for using the obtained crude IPA, the crude IPA was subjected to pressure distillation in the same manner as in Example 1, and a second distillate was extracted. The ratio of butyl formate to IPA in the second distillate was analyzed, and the result was 8 ppb.

[0070] The second distillate was filtered using four types of filters: a 100 nm pore size filter, a 10 nm pore size filter, a cation exchange filter, and a 2 nm pore size filter (manufactured by Entegris). The proportions of impurities in the purified IPA relative to the IPA were as follows: butyl formate 8 ppb, formate ions 0.5 ppb, 1-butanol 2 ppb, and trimethylsilyl IPA less than 0.1 ppb.

[0071] Explanation of reference numerals in the attached figures 1: Low-boiling distillation column 2: Condenser 3: Base of the tower 4: Water content adjustment solution 5: Distillate 6: Bottom liquid

Claims

1. A production method of purified isopropanol, which is a method of producing purified isopropanol from crude isopropanol containing butyl formate as an impurity, the method comprising a pressurized distillation step of subjecting the aforementioned crude isopropanol to pressurized distillation.

2. The method of producing purified isopropyl alcohol according to claim 1, wherein, The proportion of butyl formate in the aforementioned crude isopropanol with respect to isopropanol is 10 mass ppb or more and 100,000 mass ppb or less.

3. The method for producing purified isopropyl alcohol according to claim 1 or 2, wherein, The aforementioned crude isopropanol is subjected to pressurized distillation under conditions of an absolute pressure of 120 kPa or more and 1,000 kPa or less.

4. The production method of purified isopropanol according to claim 1, further comprising a dehydration step of dehydrating crude isopropanol raw liquid containing formate ions, 1-butanol, and water to obtain the aforementioned crude isopropanol.

5. The method of producing purified isopropyl alcohol according to claim 4, wherein, The proportion of formate ions in the aforementioned crude isopropanol raw liquid with respect to isopropanol is 10 mass ppb or more and 100,000 mass ppb or less.

6. The method for producing purified isopropyl alcohol according to claim 4 or 5, wherein, The proportion of 1-butanol in the aforementioned crude isopropanol raw liquid with respect to isopropanol is 10 mass ppb or more and 100,000 mass ppb or less.

7. The method of producing purified isopropyl alcohol according to claim 4, wherein, The aforementioned crude isopropanol raw liquid is a waste liquid recovered from a semiconductor manufacturing apparatus.

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