JP7577509B2 - Method for purifying organic solvents - Google Patents

Description

The present invention relates to a method for purifying an organic solvent to obtain a high-purity organic solvent with a reduced content of metal impurities.

ICP-MS is used to analyze trace metals in organic solvents. When using ICP-MS to analyze metals in the organic solvent to be measured, a standard solution to which metals have been added at known concentrations is diluted in several stages with a blank solution of the same type of organic solvent as the material to be measured to create a calibration curve. At this time, the metal concentration in the organic solvent to be measured is set so that it falls within the calibration curve concentration range. This method is called the absolute calibration curve method, and it is important that the blank solution does not contain the metal to be measured. This is because if the metal concentration in the blank solution is high, the background concentration will be high, raising the lower limit of quantification.

For this reason, the metal impurity content in blank solutions used in trace metal analysis of organic solvents by ICP-MS is required to be 1 ppt or less.

In addition, in the semiconductor manufacturing process, metal impurities contained in isopropyl alcohol (IPA) used for cleaning are likely to have adverse effects on the wafer, so the impurity content in IPA must be reduced to the ppt level or below 1 ppt.

As a method for purifying an organic solvent, for example, Patent Document 1 discloses a method for removing ionic contaminants from a hydrolyzable organic solvent, which includes contacting the hydrolyzable organic solvent with a mixed bed of ion exchange resins including a cation exchange resin and an anion exchange resin, and the anion exchange resin is selected from weakly basic anion exchange resins.

Furthermore, Patent Document 2 discloses a method for removing ionic contaminants from a hydrophilic organic solvent, the method comprising contacting the hydrophilic organic solvent with a mixed bed of ion exchange resins containing a cationic ion exchange resin and an anionic ion exchange resin, in which (a) the cationic ion exchange resin is a hydrogen (H)-type strong acid cationic ion exchange resin having a water retention capacity of 40 to 55% by weight, and (b) both the cationic ion exchange resin and the anionic ion exchange resin have a porosity of 0.001 to 0.1 cm ³ /g, an average pore size of 0.001 to 1.7 nm, and a BET surface area of 0.001 to 10 m ² /g.

In Patent Documents 1 and 2, the organic solvent is purified by contacting the organic solvent with a mixed bed of ion exchange resins containing a cation exchange resin and an anion exchange resin.

Special table 2019-509165 publication Special table 2019-509882 publication

However, although the methods described in Patent Documents 1 and 2 can remove metal impurities from organic solvents, there are cases where even higher purity is required. In other words, there is a demand for a method of purifying organic solvents that is even better at removing metal impurities.

In addition, because ion exchange resins contain moisture, even if an organic solvent is purified using ion exchange resins, moisture will be mixed into the resulting treatment liquid. When a high-purity organic solvent is required, even a small amount of moisture can cause problems as it can be mixed in as an impurity.

In addition to the removal of impurities, the diffusion rate of metal impurities is slow in organic solvents, and the reaction rate of the ion exchange reaction with ion exchange resins is also slow. Therefore, when removing ionic metal impurities from organic solvents using ion exchange resins, the flow rate through the ion exchange resin must be set lower than when removing ionic metal impurities from an aqueous solution. For example, when treating with a strongly acidic cation exchange resin, it is difficult to obtain the same metal removal rate at the same flow rate as in water.

As a result, in order to purify ionic metal impurities in organic solvents using ion exchange resins, the flow rate through the ion exchange resin must be set low, resulting in a problem of low purification efficiency.

Therefore, the first object of the present invention is to provide a method for purifying an organic solvent that is excellent in removing metal impurities and water from the organic solvent. The second object of the present invention is to provide a method for purifying an organic solvent that is excellent in removing metal impurities and water from the organic solvent and has high purification efficiency.

In light of this technical background, the inventors conducted extensive research and discovered that by carrying out an ion exchange treatment process in which the organic solvent to be treated is brought into contact with an ion exchange resin, followed by a distillation process in which the treatment liquid from the ion exchange treatment process is distilled, the removability of ionic metal impurities is improved and it is also possible to remove metal particles and moisture that could not be removed by the ion exchange resin, leading to the completion of the present invention.

That is, the present invention (1) comprises a first treatment step of contacting an organic solvent containing monovalent ionic metal impurities and divalent ionic metal impurities with an H-type chelate exchanger (1) at a flow rate (SV) of 2 to 30 h ^-1 ;
a second treatment step in which the treated liquid from the first treatment step is contacted with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3) at a liquid passage rate (SV) of 2 to 50 h ^;
an ion exchange treatment step comprising :
a distillation step of distilling the treated liquid from the ion exchange treatment step;
The present invention provides a method for purifying an organic solvent, comprising the steps of:
The present invention (2) also provides an ion exchange treatment step in which an organic solvent containing monovalent ionic metal impurities and divalent ionic metal impurities is contacted with a mixed bed of an H-type chelate exchanger, an anion exchanger and an H-type strongly acidic cation exchanger at a flow rate (SV) of 2 to 30 h ^-1 ;
a distillation step of distilling the treated liquid from the ion exchange treatment step;
The present invention provides a method for purifying an organic solvent, comprising the steps of:

According to the present invention, it is possible to provide a method for purifying an organic solvent that is excellent in removing metal impurities and water from the organic solvent. In addition, according to the present invention, it is possible to provide a method for purifying an organic solvent that is excellent in removing metal impurities and water from the organic solvent and has high purification efficiency.

The method for purifying an organic solvent of the present invention includes an ion exchange treatment step of contacting an organic solvent to be treated with an ion exchanger;
a distillation step of distilling the treated liquid from the ion exchange treatment step;
The method for purifying an organic solvent is characterized by comprising the steps of:

The method for purifying an organic solvent of the present invention includes at least an ion exchange process and a distillation process.

The ion exchange treatment process is a process in which the organic solvent to be treated is brought into contact with an ion exchanger.

The organic solvent to be treated in the organic solvent purification method of the present invention is not particularly limited, but examples thereof include alcohols such as isopropyl alcohol, methanol, and ethanol, ketones such as cyclohexanenone, methyl isobutyl ketone, acetone, and methyl ethyl ketone, alkene-based organic solvents such as 2,4-diphenyl-4-methyl-1-pentene and 2-phenyl-1-propene, N-methylpyrrolidone, and mixed organic solvents thereof. The organic solvent to be treated may be either a polar organic solvent or a nonpolar organic solvent, with a polar organic solvent being preferred. In addition, the polar organic solvent may be either a protic polar organic solvent or an aprotic polar organic solvent.

The treated organic solvent contains, as metal impurities, monovalent ionic metal impurities such as Na, K, and Li, and divalent or higher ionic metal impurities such as Cr, As, Ca, Cu, Fe, Mg, Mn, Ni, Pb, and Zn.

The content of each metal impurity in the organic solvent to be treated is not particularly limited, but is usually about 100 ppb to 20 ppt by mass.

Ion exchangers used in the method for purifying an organic solvent of the present invention include H-type cation exchangers and anion exchangers. Examples of H-type cation exchangers include H-type chelate exchangers and H-type strongly acidic cation exchangers. Examples of anion exchangers include strongly basic anion exchangers and weakly basic anion exchangers.

The H-type chelate exchanger is a chelate exchanger in the metal ion form, such as Na-type, Ca-type, or Mg-type, that is converted to the H-type by contacting it with a mineral acid and treating it with an acid. In other words, the H-type chelate exchanger is a mineral acid contact treatment product of a metal ion form chelate exchanger.

The functional group of the H-type chelate exchanger is not particularly limited as long as it can coordinate to a metal ion to form a chelate, and examples of such functional groups include functional groups having an amino group, such as iminodiacetic acid groups, aminomethyl phosphate groups, and iminopropionic acid groups, and thiol groups. Of these, functional groups having an amino group are preferred as the functional group of the chelate exchanger, since they enhance the removal of many polyvalent metal ions, and iminodiacetic acid groups, aminomethyl phosphate groups, and iminopropionic acid groups are particularly preferred.

The H-type chelate exchanger may be a granular H-type chelate exchange resin. The substrate of the H-type chelate exchange resin may be a styrene-divinylbenzene copolymer. The H-type chelate exchange resin may have any of a gel structure, a macroporous structure, and a porous structure. The exchange capacity of the H-type chelate exchange resin is preferably 0.5 to 2.5 eq/L-R, and more preferably 1.0 to 2.5 eq/L-R. The average particle size (harmonic mean diameter) of the H-type chelate exchange resin is not particularly limited, but is preferably 300 to 1000 μm, and more preferably 500 to 800 μm. The average particle size of the H-type chelate exchange resin is a value measured by a laser diffraction particle size distribution measuring device.

An example of an H-type chelate exchanger is an H-type organic porous chelate exchanger. An H-type organic porous chelate exchanger is an organic porous material into which a functional group having chelating ability, such as the functional groups having chelating ability listed above, has been introduced. The exchange capacity of the H-type organic porous chelate exchanger is preferably 0.3 to 2 mg equivalents/mL (in a water-wet state), and particularly preferably 1 to 2 mg equivalents/mL (in a water-wet state).

The H-type chelate exchanger can be obtained by contacting a metal ion type chelate exchanger, such as a Na-type, Ca-type, or Mg-type, with a mineral acid for acid treatment. Examples of mineral acids that can be contacted with a metal ion type chelate exchanger include hydrochloric acid, sulfuric acid, and nitric acid. Of these, hydrochloric acid and sulfuric acid are preferred from the viewpoint of safety. In addition, in the case of conversion from a Ca-type, hydrochloric acid is preferred because there is a risk of calcium sulfate precipitation. The concentration of the mineral acid is preferably 0.1 to 6N, and particularly preferably 1 to 4N.

There are no particular limitations on the method for contacting the mineral acid with the metal ion-type chelate exchanger, and the contact method, contact temperature, contact time, etc. may be appropriately selected.

After contacting the metal ion chelate exchanger with mineral acid, the H-type chelate exchanger that has been converted to H-type is washed with water to remove excess mineral acid. However, since the functional groups in the chelate exchanger are bonded to the mineral acid by hydrogen bonds, etc., the excess mineral acid cannot be completely removed by washing with water. Therefore, the mineral acid used in the acid treatment remains in the H-type chelate exchanger.

For example, metal ion type chelate exchange resins include CR-10 and CR-11 manufactured by Mitsubishi Chemical Corporation, Duolite C-467 manufactured by Sumika Chemtex Corporation, MC-700 manufactured by Sumitomo Chemical Co., Ltd., Lewatit TP207, Lewatit TP208, and Lewatit TP260 manufactured by Lanxess AG, S930 and S950 manufactured by Purolite Corporation, and DS-21 and DS-22 manufactured by Organo.

H-type strongly acidic cation exchangers are those in which strongly acidic cation exchange groups such as sulfonic acid groups have been converted to the H-type.

Examples of H-type strongly acidic cation exchangers include granular strongly acidic cation exchange resins. The substrate of the H-type strongly acidic cation exchange resin is a styrene-divinylbenzene copolymer. The H-type strongly acidic cation exchange resin may have any of a gel structure, a macroporous structure, and a porous structure. The ion exchange capacity of the H-type strongly acidic cation exchange resin in a wet state is preferably 0.5 (eq/L-R) or more, and particularly preferably 1.0 (eq/L-R) or more. The ion exchange capacity of the H-type strongly acidic cation exchange resin in a wet state is preferably as high as possible, and is appropriately selected. The harmonic mean diameter of the H-type strongly acidic cation exchange resin is preferably 200 to 900 μm, and particularly preferably 300 to 600 μm. Examples of H-type strong acid cation exchange resins include Amberlite IR120B, IR124, 200CT252, Amberjet 1020, 1024, 1060, and 1220 manufactured by The Dow Chemical Company, and Diaion SK104, SK1B, SK110, SK112, PK208, PK212L, PK216, and PK220 manufactured by Mitsubishi Chemical Corporation. 18, PK220, PK228, UBK08, UBK10, UBK12, Organo's DS-1, DS-4, Purolite's C100, C100E, C120E, C100x10, C100x12MB, C150, C160, SGC650, Lewatit's Monoplus S108H, SP112, S1668, etc.

An example of an H-type strongly acidic cation exchanger is an H-type organic porous strongly acidic cation exchanger. An H-type organic porous strongly acidic cation exchanger is an organic porous material into which a strongly acidic cation exchange group, such as the strongly acidic cation exchange group listed above, has been introduced. The exchange capacity of the H-type organic porous strongly acidic cation exchanger is preferably 1 to 3 mg equivalents/mL (dry state), and particularly preferably 1.5 to 3 mg equivalents/mL (dry state).

Anion exchangers are classified into two types: strongly basic anion exchangers that have strongly basic anion exchange groups as anion exchange groups, and weakly basic anion exchangers that have weakly basic anion exchange groups as anion exchange groups.

Strongly basic anion exchange groups related to strongly basic anion exchangers include OH-type quaternary ammonium groups. Weakly basic anion exchange groups related to weakly basic anion exchangers include tertiary amino groups, secondary amino groups, primary amino groups, polyamine groups, etc. In addition, for highly basic OH-type anion exchangers, carbonate or bicarbonate anion exchangers with low basicity may be used in solvents where decomposition or chemical reactions may occur.

An example of an anion exchanger is a granular anion exchange resin. The substrate of the anion exchange resin is a styrene-divinylbenzene copolymer. The anion exchange resin may have any of a gel structure, a macroporous structure, and a porous structure. The ion exchange capacity of the anion exchange resin in a wet state is preferably 0.5 to 2 (eq/L-R), and more preferably 0.9 to 2 (eq/L-R). The harmonic mean diameter of the anion exchange resin is preferably 200 to 900 μm, and more preferably 300 to 800 μm. Examples of anion exchange resins include Amberlite IRA900, 402, 96SB, 98, Amberjet 4400, 4002, and 4010 manufactured by Dow Chemical Company; Diaion UBA120, PA306S, PA308, PA312, PA316, PA318L, WA21J, and WA30 manufactured by Mitsubishi Chemical Corporation; DS-2, DS-5, and DS-6 manufactured by Organo Corporation; A400, A600, SGA550, A500, A501P, A502PS, A503, A100, A103S, A110, A111S, and A133S manufactured by Purolite Corporation; and Monoplus M500, M800, MP62WS, and MP64 manufactured by Lewatit Corporation.

Another example of an anion exchanger is an organic porous anion exchanger. The organic porous anion exchanger is an organic porous material into which an anion exchange group, such as the strongly basic anion exchange group or the weakly basic anion exchange group listed above, has been introduced. The exchange capacity of the organic porous anion exchanger is preferably 1 to 6 mg equivalents/mL (dry state), and particularly preferably 2 to 5 mg equivalents/mL (dry state).

In the ion exchange treatment process, the organic solvent to be treated is brought into contact with at least an H-type cation exchanger, preferably an H-type strongly acidic cation exchanger.

The H-type cation exchanger and H-type strongly acidic cation exchanger involved in the ion exchange treatment process are the H-type cation exchanger and H-type strongly acidic cation exchanger described above.

The first type of ion exchange treatment step (hereinafter also referred to as ion exchange treatment step (1)) has a treatment step of contacting the organic solvent to be treated with an H-type strongly acidic cation exchanger and an anion exchanger. The anion exchanger in the ion exchange treatment step (1) may be a strongly basic anion exchanger or a weakly basic anion exchanger.

The H-type strongly acidic cation exchanger, anion exchanger, strongly basic anion exchanger, and weakly basic anion exchanger in the ion exchange treatment step (1) are the H-type strongly acidic cation exchanger, anion exchanger, strongly basic anion exchanger, and weakly basic anion exchanger described above.

In the ion exchange treatment step (1), the method of contacting the organic solvent to be treated with the H-type strongly acidic cation exchanger and the anion exchanger is not particularly limited, and examples thereof include (i) a method of passing the organic solvent to be treated through a mixed bed of an H-type strongly acidic cation exchanger and an anion exchanger, (ii) a method of passing the organic solvent to be treated through a double bed consisting of an H-type strongly acidic cation exchanger layer in the front stage and an anion exchanger layer in the rear stage, and (iii) a method of first passing the organic solvent to be treated through a single bed of the H-type strongly acidic cation exchanger in the front stage, and then passing the treated liquid through a single bed of the anion exchanger in the rear stage. (iv) first, the organic solvent to be treated is passed through a single bed of an anion exchanger in the first stage, and then the treated liquid is passed through a single bed of an H-type strongly acidic cation exchanger in the second stage; (v) the organic solvent to be treated is passed through a multiple bed in which the repeating units of the single bed of an anion exchanger in the first stage and the single bed of an anion exchanger in the second stage are repeated in two or more sets; (vi) the organic solvent to be treated is passed through a multiple bed in which the repeating units of the single bed of an anion exchanger in the first stage and the single bed of an H-type strongly acidic cation exchanger in the second stage are repeated in two or more sets. The mixed bed of an H-type strongly acidic cation exchanger and anion exchanger is composed of a mixture of an H-type strongly acidic cation exchanger and an anion exchanger. When the H-type strongly acidic cation exchanger is an H-type strongly acidic organic porous cation exchanger, a shape cut to an arbitrary size, for example, a cube with one side of about 3 mm to about 10 mm, is used. In addition, when the anion exchanger is an organic porous strongly acidic anion exchanger, an organic porous anion exchanger cut to any size is used, for example, a cube with one side of about 3 mm to about 10 mm.

In the ion exchange treatment step (1), the flow rate (SV) when the organic solvent to be treated is passed through the H-type strongly acidic cation exchanger and the anion exchanger is not particularly limited and may be appropriately selected, but is preferably 0.1 to 50 h ^-1 , particularly preferably 2 to 30 h ^-1 , and further preferably 4 to 25 h ^-1 .

In the ion exchange treatment step (1), the temperature at which the organic solvent to be treated is passed through the H-type strongly acidic cation exchanger and the anion exchanger is not particularly limited and may be appropriately selected, but is usually 0 to 50°C.

The second type of ion exchange treatment step (hereinafter also referred to as ion exchange treatment step (2)) comprises a first treatment step of contacting the organic solvent to be treated with an H-type chelate exchanger (1a);
a second treatment step in which the treatment liquid from the first treatment step is contacted with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3);
has.

The H-type chelate exchanger, anion exchanger, and H-type strongly acidic cation exchanger involved in the ion exchange treatment step (2) are the H-type chelate exchanger, anion exchanger, and H-type strongly acidic cation exchanger described above.

The first treatment step in the ion exchange treatment step (2) is to contact the organic solvent to be treated with an H-type chelate exchanger (1a).

In the first treatment step related to the ion exchange treatment step (2), the organic solvent to be treated is treated with the H-type chelate exchanger (1a) by contacting the organic solvent to be treated with the H-type chelate exchanger (1a), and mainly divalent or higher metals and some of the monovalent metals in the organic solvent to be treated are removed.

In the first treatment step relating to the ion exchange treatment step (2), the flow rate (SV) when the organic solvent to be treated is passed through the H-type chelate exchanger (1a) is not particularly limited and may be appropriately selected, but is preferably 0.1 to 50 h ^-1 , particularly preferably 2 to 30 h ^-1 , and further preferably 4 to 25 h ^-1 .

In the first treatment step related to the ion exchange treatment step (2), the temperature at which the organic solvent to be treated is passed through the H-type chelate exchanger (1a) is not particularly limited and may be selected as appropriate, but is usually 0 to 50°C. Depending on the type of organic solvent to be treated, the organic solvent to be treated may be passed through the H-type chelate exchanger (1a) at 0 to 80°C in the first treatment step.

The second treatment step related to the ion exchange treatment step (2) is a step in which the treatment liquid from the first treatment step is brought into contact with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3).

In the second treatment step related to the ion exchange treatment step (2), the treatment liquid from the first treatment step is brought into contact with the anion exchanger (2) and the H-type strongly acidic cation exchanger (3), thereby treating the organic solvent to be treated with the anion exchanger (2) and the H-type strongly acidic cation exchanger (3), and removing the remaining monovalent metals that could not be removed by the H-type chelate exchanger (1a) in the first treatment step and the mineral acid released from the H-type chelate exchanger (1a). In addition, NaOH is used as a regenerant to regenerate the anion exchanger, but if it is thoroughly washed after regeneration, there is almost no chance of NaOH remaining in the anion exchanger. In the second treatment step, even if the washing after regeneration of the anion exchanger (2) is poor and the residue of NaOH used as the regenerant is eluted from the anion exchanger (2), the H-type strongly acidic cation exchanger (3) in the second treatment step can remove Na.

In the second treatment step related to the ion exchange treatment step (2), the liquid passage speed (SV) when the treatment liquid of the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is preferably 0.1 to 100 h ^-1 , particularly preferably 2 to 50 h ^-1 .

In the second treatment step related to the ion exchange treatment step (2), the temperature at which the treatment liquid from the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is usually 0 to 50°C. Depending on the type of organic solvent to be treated, the treatment liquid from the first treatment step may be passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) at 0 to 80°C in the second treatment step. When the treatment liquid from the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) at 60 to 80°C in the second treatment step, if a strongly basic anion exchanger (2a) is used as the anion exchanger (2), the strongly basic anion exchanger (2a) is easily decomposed, so a weakly basic anion exchanger (2b) is used as the anion exchanger (2).

In the ion exchange treatment step (2), the method of contacting the treatment liquid from the first step with the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited, and examples thereof include (i) a method of passing the organic solvent to be treated through a mixed bed of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3), (ii) a method of passing the organic solvent to be treated through a double bed consisting of a layer of the anion exchanger (2) on the front side and a layer of the H-type strongly acidic cation exchanger (3) on the rear side, and (iii) a method of first passing the organic solvent to be treated through a single bed of the anion exchanger (2) on the front side and then passing the treatment liquid through a layer of the H-type strongly acidic cation exchanger (3) on the rear side. (iv) a method of first passing the organic solvent to be treated through a single bed of the H-type strongly acidic cation exchanger (3) in the front stage and then passing the treated liquid through a single bed of the anion exchanger (2) in the rear stage, (v) a method of passing the organic solvent to be treated through a multiple bed in which the repeating units of the single bed of the anion exchanger (2) in the front stage and the single bed of the H-type strongly acidic cation exchanger (3) in the rear stage are repeated in two or more sets, and (vi) a method of passing the organic solvent to be treated through a multiple bed in which the repeating units of the single bed of the H-type strongly acidic cation exchanger (3) in the front stage and the single bed of the anion exchanger (2) in the rear stage are repeated in two or more sets. The mixed bed of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) consists of a mixture of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3). When the anion exchanger (2) is an organic porous anion exchanger, an organic porous anion exchanger cut to any size, for example, a cubic shape with a side of about 3 mm to about 10 mm, is used. When the H-type strongly acidic cation exchanger (3) is an organic porous strongly acidic cation exchanger, an organic porous strongly acidic cation exchanger cut to any size, for example, a cubic shape with a side of about 3 mm to about 10 mm, is used.

The third embodiment of the ion exchange treatment step (hereinafter also referred to as ion exchange treatment step (3)) comprises a first treatment step of contacting the organic solvent to be treated with an H-type strongly acidic cation exchanger (1b);
a second treatment step in which the treatment liquid from the first treatment step is contacted with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3);
has.

The H-type strongly acidic cation exchanger and anion exchanger involved in the ion exchange treatment step (3) are the H-type strongly acidic cation exchanger and anion exchanger described above.

The first treatment step in the ion exchange treatment step (3) is a step in which the organic solvent to be treated is brought into contact with an H-type strongly acidic cation exchanger (1b).

In the first treatment step related to the ion exchange treatment step (3), the organic solvent to be treated is treated with the H-type strongly acidic cation exchanger (1b) by contacting the organic solvent to be treated with the H-type strongly acidic cation exchanger (1b), and a portion of the divalent or higher metals and a portion of the monovalent metals in the organic solvent to be treated are removed.

In the first treatment step relating to the ion exchange treatment step (3), the flow rate (SV) when the organic solvent to be treated is passed through the H-type strongly acidic cation exchanger (1b) is not particularly limited and may be appropriately selected, but is preferably 0.1 to 100 h ^-1 , particularly preferably 2 to 50 h ^-1 .

In the first treatment step related to the ion exchange treatment step (3), the temperature at which the organic solvent to be treated is passed through the H-type strongly acidic cation exchanger (1b) is not particularly limited and may be selected as appropriate, but is usually 0 to 50°C. Depending on the type of organic solvent to be treated, the organic solvent to be treated may be passed through the H-type strongly acidic cation exchanger (1b) at 0 to 80°C in the first treatment step.

The second treatment step related to the ion exchange treatment step (3) is a step in which the treatment liquid from the first treatment step is brought into contact with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3).

In the ion exchange treatment step (3), the H-type strongly acidic cation exchanger (1b) used in the first treatment step and the H-type strongly acidic cation exchanger (3) used in the second treatment step may be the same type of H-type strongly acidic cation exchanger or different types of H-type strongly acidic cation exchangers.

In the second treatment step related to the ion exchange treatment step (3), the treatment liquid from the first treatment step is brought into contact with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3), thereby treating the organic solvent to be treated with the anion exchanger (2) and the H-type strongly acidic cation exchanger (3), and removing the remainder of divalent or higher metals and monovalent metals that could not be completely removed by the H-type strongly acidic cation exchanger (1b) in the first treatment step. In addition, in the second treatment step, the anion exchanger removes metals that may have metal ions in the anionic form, such as Cr and As, and acids such as mineral acids and organic acids.

In the ion exchange treatment step (3), the organic solvent to be treated is first contacted with an H-type strongly acidic cation exchanger, and then contacted again with an H-type strongly acidic cation exchanger, thus performing two or more contact steps, thereby increasing the removal rate of divalent or higher metals compared to the case where the organic solvent to be treated is contacted with the same amount of an H-type strongly acidic cation exchanger.

In the second treatment step relating to the ion exchange treatment step (3), the liquid passage speed (SV) when the treatment liquid of the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is preferably 0.1 to 100 h ^-1 , particularly preferably 2 to 50 h ^-1 .

In the second treatment step related to the ion exchange treatment step (3), the temperature at which the treatment liquid from the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is usually 0 to 50°C. Depending on the type of organic solvent to be treated, the treatment liquid from the first treatment step may be passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) at 0 to 80°C in the second treatment step. When the treatment liquid from the first treatment step is passed through the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) at 0 to 80°C in the second treatment step, if a strongly basic anion exchanger (2a) is used as the anion exchanger (2), the strongly basic anion exchanger (2a) is easily decomposed, so a weakly basic anion exchanger (2b) is used as the anion exchanger (2).

In the ion exchange treatment step (3), the method of contacting the treatment liquid from the first step with the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited, and examples thereof include (i) a method of passing the organic solvent to be treated through a mixed bed of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3), (ii) a method of passing the organic solvent to be treated through a double bed consisting of a layer of the anion exchanger (2) on the front side and a layer of the H-type strongly acidic cation exchanger (3) on the rear side, and (iii) a method of first passing the organic solvent to be treated through a single bed of the anion exchanger (2) on the front side and then passing the treatment liquid through a layer of the H-type strongly acidic cation exchanger (3) on the rear side. (iv) a method of first passing the organic solvent to be treated through a single bed of the H-type strongly acidic cation exchanger (3) in the front stage and then passing the treated liquid through a single bed of the anion exchanger (2) in the rear stage, (v) a method of passing the organic solvent to be treated through a multiple bed in which the repeating units of the single bed of the anion exchanger (2) in the front stage and the single bed of the H-type strongly acidic cation exchanger (3) in the rear stage are repeated in two or more sets, and (vi) a method of passing the organic solvent to be treated through a multiple bed in which the repeating units of the single bed of the H-type strongly acidic cation exchanger (3) in the front stage and the single bed of the anion exchanger (2) in the rear stage are repeated in two or more sets. The mixed bed of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) consists of a mixture of the anion exchanger (2) and the H-type strongly acidic cation exchanger (3). When the anion exchanger (2) is an organic porous anion exchanger, an organic porous anion exchanger cut to any size, for example, a cubic shape with a side of about 3 mm to about 10 mm, is used. When the H-type strongly acidic cation exchanger (3) is an organic porous strongly acidic cation exchanger, an organic porous strongly acidic cation exchanger cut to any size, for example, a cubic shape with a side of about 3 mm to about 10 mm, is used.

The fourth form of the ion exchange treatment step (hereinafter also referred to as ion exchange treatment step (4)) has a treatment step (3) in which the organic solvent to be treated is brought into contact with a mixed bed of an H-type chelate exchanger (1a), an anion exchanger (2), and an H-type strongly acidic cation exchanger (3).

The H-type chelate exchanger, anion exchanger, and H-type strongly acidic cation exchanger involved in the ion exchange treatment step (4) are the H-type chelate exchanger, anion exchanger, and H-type strongly acidic cation exchanger described above.

The ion exchange treatment step (4) is a step in which the organic solvent to be treated is brought into contact with a mixed bed of an H-type chelate exchanger (1a), an anion exchanger (2), and an H-type strongly acidic cation exchanger (3).

The mixed bed of the H-type chelate exchanger (1a), anion exchanger (2) and H-type strongly acidic cation exchanger (3) in the ion exchange treatment step (4) is composed of a mixture of the H-type chelate exchanger (1a), anion exchanger (2) and H-type strongly acidic cation exchanger (3). When the H-type chelate exchanger (1a) is an H-type organic porous chelate exchanger, an H-type organic porous strongly acidic chelate exchanger cut into any size, for example, a cubic H-type chelate exchanger with a side length of about 3 mm to about 10 mm, is used. When the anion exchanger (2) is an organic porous anion exchanger, an organic porous anion exchanger cut into any size, for example, a cubic H-type cation exchanger with a side length of about 3 mm to about 10 mm, is used. When the H-type strongly acidic cation exchanger (3) is an organic porous strongly acidic cation exchanger, an organic porous strongly acidic cation exchanger cut into any size, for example, a cubic H-type cation exchanger with a side length of about 3 mm to about 10 mm, is used.

In the ion exchange treatment step (4), the organic solvent to be treated is treated with a mixed bed of H-type chelate exchanger (1a), anion exchanger (2), and H-type strongly acidic cation exchanger (3) by contacting the organic solvent to be treated with the mixed bed of H-type chelate exchanger (1a), anion exchanger (2), and H-type strongly acidic cation exchanger (3), and divalent or higher metals and monovalent metals in the organic solvent to be treated are removed. In the treatment step (3), the anion exchanger (2) removes mineral acids released from the H-type chelate exchanger (1a) into the organic solvent to be treated.

In the ion exchange treatment step (4), the flow rate (SV) at which the organic solvent to be treated is passed through the mixed bed of the H-type chelate exchanger (1a), the anion exchanger (2) and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is preferably 0.1 to 50 h ^-1 , particularly preferably 2 to 30 h ^-1 , and further preferably 4 to 25 h ^-1 .

In the ion exchange treatment step (4), the temperature at which the organic solvent to be treated is passed through the mixed bed (3) of the H-type chelate exchanger (1a), the anion exchanger (2), and the H-type strongly acidic cation exchanger (3) is not particularly limited and may be appropriately selected, but is usually 0 to 50°C. Depending on the type of organic solvent to be treated, the organic solvent to be treated may be passed through the mixed bed of the H-type chelate exchanger (1a), the anion exchanger (2), and the H-type strongly acidic cation exchanger (3) at 0 to 80°C in the ion exchange treatment step (4). In the ion exchange treatment step (4), when the organic solvent to be treated is passed through a mixed bed of H-type chelate exchanger (1a), anion exchanger (2), and H-type strongly acidic cation exchanger (3) at 0 to 80°C, if a strongly basic anion exchanger (2a) is used as the anion exchanger (2), the strongly basic anion exchanger (2a) is easily decomposed, so a weakly basic anion exchanger (2b) is used as the anion exchanger (2).

In the ion exchange treatment step (2) or the ion exchange treatment step (4), the ratio of the volume of the anion exchanger (2) to the volume of the H-type chelate exchanger (1a) ((volume of anion exchanger (2)/volume of H-type chelate exchanger (1a)) x 100) is preferably 0.1 to 99.0 vol%, more preferably 0.1 to 70.0 vol%, and particularly preferably 0.1 to 50.0 vol%.

In the ion exchange treatment step (2) or the ion exchange treatment step (4), the ratio of the volume of the strongly acidic cation exchanger (3) to the volume of the H-type chelate exchanger (1a) ((volume of strongly acidic cation exchanger (3)/volume of H-type chelate exchanger (1a)) x 100) is preferably 0.1 to 99.0 vol%, more preferably 0.1 to 70.0 vol%, and particularly preferably 0.1 to 50.0 vol%.

For the H-type cation exchangers (H-type chelate exchanger (1a), strongly acidic cation exchanger (1b)), anion exchanger (2) and H-type strongly acidic cation exchanger (3), the substrate into which the ion exchange groups are introduced may be an organic porous material. The organic porous material according to the present invention is described below.

The organic porous ion exchanger has an H-type chelate exchange group, a strong acid cation group, or an anion exchange group introduced therein. That is, an organic porous ion exchanger having an H-type chelate exchange group introduced therein is an H-type organic porous chelate exchanger (1a), an organic porous ion exchanger having an H-type strong acid cation exchange group introduced therein is an H-type organic porous strong acid cation exchanger (1b) or (3), and an organic porous ion exchanger having an anion exchange group introduced therein is an organic porous anion exchanger. The functional groups introduced into the organic porous ion exchanger are the same as those introduced into the above-mentioned H-type cation exchanger (H-type chelate exchanger (1a), strong acid cation exchanger (1b)), anion exchanger (2), or H-type strong acid cation exchanger (3).

The organic porous ion exchanger may be, for example, an organic porous ion exchanger (hereinafter also referred to as a first form of organic porous ion exchanger) that is composed of a continuous skeleton phase and a continuous pore phase, the thickness of the continuous skeleton being 1 to 100 μm, the average diameter of the continuous pores being 1 to 1000 μm, the total pore volume being 0.5 to 50 mL/g, and that has ion exchange groups (chelate exchange groups, H-type strongly acidic cation exchange groups, or anion exchange groups) introduced therein, has an ion exchange capacity per weight in a dry state of 1 to 6 mg equivalents/g, and the ion exchange groups are uniformly distributed throughout the organic porous ion exchanger.

The first type of organic porous ion exchanger is an organic porous ion exchanger having an open cell structure in which bubble-like macropores overlap each other and the overlapping portions form openings with an average diameter of 1 to 1000 μm, a total pore volume of 1 to 50 mL/g, ion exchange groups introduced therein, an ion exchange capacity per weight in a dry state of 1 to 6 mg equivalents/g, and ion exchange groups uniformly distributed throughout the organic porous ion exchanger.

The first type of organic porous ion exchanger may be an organic porous ion exchanger having a continuous macropore structure in which bubble-like macropores overlap each other and the overlapping portions form openings with an average diameter of 30 to 300 μm, a total pore volume of 0.5 to 10 ml/g, cation exchange groups or anion exchange groups introduced, an ion exchange capacity per weight in a dry state of 1 to 6 mg equivalents/g, ion exchange groups uniformly distributed in the organic porous ion exchanger, and in an SEM image of a cut surface of the continuous macropore structure (dried body), the area of the skeleton portion appearing in the cross section is 25 to 50% of the image area.

In addition, the organic porous ion exchanger of the first embodiment is an organic porous ion exchanger in which the organic porous ion exchanger is a bicontinuous structure consisting of a three-dimensionally continuous skeleton with an average thickness of 1 to 60 μm made of an aromatic vinyl polymer containing 0.1 to 5.0 mol % of crosslinked structural units among all structural units into which ion exchange groups (chelate exchange groups, H-type strongly acidic cation exchange groups, or anion exchange groups) have been introduced, and three-dimensionally continuous pores with an average diameter of 10 to 200 μm are formed between the skeletons, the total pore volume is 0.5 to 10 mL/g, cation exchange groups have been introduced, the ion exchange capacity per weight in a dry state is 1 to 6 mg equivalents/g, and the ion exchange groups are uniformly distributed in the organic porous ion exchanger.

The distillation process is a process of distilling the treated liquid obtained by carrying out the ion exchange process.

In the distillation process, the method of distilling the treated liquid of the ion exchange treatment process is not particularly limited, and examples of simple distillation include a method of distilling the treated liquid of the ion exchange treatment process using a boiling distillation apparatus and a method of distilling the treated liquid of the ion exchange treatment process using a non-boiling distillation apparatus. As a distillation method, precision distillation or reduced pressure or vacuum distillation may be used. As a distillation method, precision distillation is preferred because of its high performance in separation and purification.

The liquid-contacting parts of the distillation apparatus are preferably made of or coated with a fluororesin such as a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene (PFA) or polytetrafluoroethylene (PTFE) in order to prevent metal elution. If there is no metal elution into the object to be removed or measured, the liquid-contacting parts may be made of or coated with a mineral such as quartz.

The distillation conditions in the distillation process are appropriately selected depending on the type of organic solvent, boiling point, impurity concentration before distillation, and target impurity reduction concentration after distillation.

When using an organic solvent that may decompose or denature due to heat, it is preferable to use a non-boiling distillation apparatus and perform distillation over a long period of time at a low temperature below the boiling point of the organic solvent. Distillation can also be performed by lowering the boiling point of the solvent using reduced pressure distillation.

The method for purifying an organic solvent of the present invention has a high ability to remove metal impurities by performing a distillation process after the ion exchange process. In addition, even if water is mixed into the organic solvent from the ion exchanger used in the ion exchange process, the method for purifying an organic solvent of the present invention has excellent water removal properties because the water can be removed in the distillation process.

In addition, because metal particles are not ions, they cannot be removed when purification is performed using only ion exchange resins. In contrast, the method for purifying organic solvents of the present invention can remove metal particles in the distillation process, which increases the removability of metal impurities.

In addition, organic solvents may contain organic impurities such as by-products generated or remaining in the manufacturing process, for example, propylene glycol monomethyl ether acetate (PGMEA) in the manufacture of propylene glycol monomethyl ether (PGME) and acetone in the manufacture of isopropyl alcohol (IPA), and eluates from resin components used in the organic solvent manufacturing or refining equipment. In the organic solvent purification method of the present invention, such organic impurities can be removed in the distillation process, thereby increasing the removability of organic impurities.

In addition, since the diffusion rate of metal impurities in organic solvents is low, and the reaction rate of the ion exchange reaction with ion exchange resins is also low, when purifying organic solvents using only ion exchange resins, it is necessary to slow down the flow rate of the organic solvent through the ion exchange resin in order to increase the removal rate of ionic metal impurities. In contrast, in the method for purifying organic solvents of the present invention, since a distillation process is performed after the ion exchange process, even if the removal rate of ionic metal impurities is reduced by increasing the flow rate of the organic solvent through the ion exchanger in the ion exchange process, the amount of ionic metal impurities removed in the ion exchange process can be covered by the distillation process by removing the ionic metal impurities in the subsequent distillation process. Therefore, in the method for purifying an organic solvent of the present invention, the rate at which the organic solvent is passed through the ion exchanger in the ion exchange treatment step can be increased to the extent that the distillation step can cover the reduced ability to remove ionic metal impurities by increasing the rate at which the organic solvent is passed through the ion exchanger in the ion exchange treatment step. Therefore, the method for purifying an organic solvent of the present invention can produce a high-purity organic solvent with high purification efficiency.

In the ion exchange treatment step of the method for purifying an organic solvent of the present invention, the ion exchange treatment steps (2) and (4) use an H-type chelate exchanger as the H-type cation exchanger. This H-type chelate exchanger has a low removal rate with a strongly acidic cation exchange resin, and is highly capable of removing divalent or higher metals such as Cr, some of which may be in an anionic form in the organic solvent. Therefore, in the ion exchange treatment step of the method for purifying an organic solvent of the present invention, the ion exchange treatment steps (2) and (4) have a high removal rate of divalent or higher metals such as Cr.

The content of each metal in the purified organic solvent obtained by carrying out the method for purifying an organic solvent of the present invention is appropriately selected depending on the use of the organic solvent after purification, and is preferably 10 ng/L or less in each case. In other words, the content of each divalent or higher metal in the purified organic solvent obtained by carrying out the method for purifying an organic solvent of the present invention is appropriately selected depending on the use of the organic solvent after purification, and is preferably 10 ng/L or less in each case, and the content of monovalent metals is appropriately selected depending on the use of the organic solvent after purification, and is preferably 10 ng/L or less in each case.

Furthermore, according to the method for purifying an organic solvent of the present invention, purification to an impurity level of 1 ng/L or less is possible, so the purified organic solvent obtained by carrying out the method for purifying an organic solvent of the present invention is preferably used as a dilution solvent for a standard solution used for preparing a calibration curve for trace metal analysis (calibration curve blank liquid), a dilution solvent for a sample, and a cleaning solvent for instruments and analytical equipment. In the method for purifying an organic solvent of the present invention, the ion exchange treatment steps (1), (2), (3), and (4) are a combination of a cation exchanger and an anion exchanger, so that in addition to ionic metal impurities, acids and anions can be removed, and therefore the method is preferably used as a calibration curve blank liquid used in ion chromatography. The uses of the purified organic solvent obtained by carrying out the method for purifying an organic solvent of the present invention include a dilution solvent, a dissolution solvent, a cleaning solvent, and a drying solvent in the semiconductor manufacturing process.

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the following examples.

<Organic solvent 1 to be treated>
A sample in which commercially available propylene glycol monomethyl ether (PGME EL grade, manufactured by Showa Denko) was hermetically stored in a metal container to increase the metal concentration was used as the treated organic solvent 1. The contents of each metal impurity are shown in Table 1.

Example 1
(Ion exchange treatment process)
A 50 mL mixture of H-form chelate exchange resin (DS-21), OH-form strongly basic anion exchange resin (DS-2), and H-form strongly acidic cation exchange resin (DS-1) in a volume ratio of 3:1:1 was packed into a column having an inner diameter of 16 mm and a height of 300 mm (H-form C/OH-form A/H-form K mixed bed 1).
Next, the organic solvent 1 to be treated was passed through the H-form C/OH-form A/H-form K mixed bed 1 at SV5 h ⁻¹ , and when 20 BV (20 times the resin volume) had been passed, 1000 mL of treated liquid was obtained.
H-type chelating exchange resin: H-type aminophosphate chelating resin, manufactured by Organo Corporation, Orlite DS-21, cation exchange capacity 1.8 eq/L-resin, harmonic mean diameter 500 μm
OH-type strongly basic anion exchange resin (DS-2): manufactured by Organo Corporation, anion exchange capacity 1.0 eq/L-resin H-type strongly acidic cation exchange resin (DS-1): manufactured by Organo Corporation, cation exchange capacity 2.0 eq/L-resin

(Distillation process)
Next, the treated liquid from the ion exchange treatment step was distilled using a non-boiling distillation apparatus (Evapoclean, manufactured by Eas Corporation) at 70° C. for 18 hours to obtain 100 mL of treated liquid.

(analysis)
The metal content of the resulting treatment liquid was then measured, and the results are shown in Table 1. The water content was also measured, and was found to be 300 ppm.
<Moisture measurement>
The moisture content was measured using an Aquacounter AQ-2200 (manufactured by Hiranuma Sangyo Co., Ltd.).

(Comparative Example 1)
An ion exchange treatment step was carried out in the same manner as in Example 1 to obtain 1000 mL of a treated liquid.
The metal content of the resulting treatment liquid was then measured, and the results are shown in Table 1. The water content was also measured, and was found to be 320 ppm by mass.
That is, in Comparative Example 1, the ion exchange treatment step was carried out, but the distillation step was not carried out.

(Comparative Example 2)
The organic solvent 1 to be treated was distilled using a non-boiling distillation apparatus (Evapoclean, manufactured by Eas Corporation) at 80° C. for 18 hours to obtain 100 mL of a treated liquid.
The metal content of the resulting treatment liquid was then measured, and the results are shown in Table 1. The water content was also measured, and was found to be 280 ppm.
That is, in Comparative Example 2, the distillation step was carried out, but the ion exchange treatment step was not carried out.

The results of Example 1 and Comparative Examples 1 and 2 show that by combining ion exchange resin purification and distillation, the metal impurity concentration can be reduced to a lower level than by either ion exchange resin purification or distillation purification alone.

Claims (2)

A first treatment step in which an organic solvent containing monovalent ionic metal impurities and divalent ionic metal impurities is contacted with an H-type chelate exchanger (1) at a flow rate (SV) of 2 to 30 h ^-1 ;
a second treatment step in which the treated liquid from the first treatment step is contacted with an anion exchanger (2) and an H-type strongly acidic cation exchanger (3) at a liquid passage rate (SV) of 2 to 50 h ^;
an ion exchange treatment step comprising :
a distillation step of distilling the treated liquid from the ion exchange treatment step;
1. A method for purifying an organic solvent, comprising the steps of: an ion exchange treatment step in which an organic solvent containing monovalent ionic metal impurities and divalent ionic metal impurities is contacted with a mixed bed of an H-type chelate exchanger, an anion exchanger and an H-type strongly acidic cation exchanger at a flow rate (SV) of 2 to 30 h ^-1 ;
a distillation step of distilling the treated liquid from the ion exchange treatment step;
1. A method for purifying an organic solvent, comprising the steps of: