Method and apparatus for purifying non-aqueous solvent

Abstract

To provide a refining method of a non-aqueous solvent using an ion exchange resin where a water content is easily and economically reduced without needing various kinds of non-aqueous solvents for pretreatment.SOLUTION: A refining method of a non-aqueous solvent using an ion exchange resin includes: a pretreatment step where the ion exchange resin is brought into contact with the non-aqueous solvent for pretreatment having a relative dielectric constant of 15 or more at 25°C; and a refining step where the ion exchange resin after the pretreatment is brought into contact with the non-aqueous solvent to be refined. A component concordance rate of the non-aqueous solvent for pretreatment and the non-aqueous solvent to be refined is 85 mass% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for purifying a non-aqueous solvent using an ion exchange resin having a reduced water content. [Background technology]

[0002] In recent years, highly purified non-aqueous solvents have been used in the manufacture of semiconductors and lithium ion batteries. Distillation is known as a method for purifying non-aqueous solvents, but it has technical issues such as high equipment costs, the need for a large amount of energy, and difficulty in achieving high-level purification. Therefore, a method for purifying non-aqueous solvents by an ion exchange method using an ion exchange resin or an ion exchange filter has been proposed. The ion exchange method has the characteristics of low equipment costs, energy saving, and enabling high-level purification.

[0003] However, since ion exchange resins usually contain moisture, there is a problem that moisture eluted from the ion exchange resin is mixed into the nonaqueous solvent when purifying the nonaqueous solvent. Therefore, it is necessary to reduce the moisture contained in the ion exchange resin before using the ion exchange resin for purifying the nonaqueous solvent. As a method for reducing the moisture content of the ion exchange resin, a method of drying the ion exchange resin under reduced pressure and a method of passing a pretreatment nonaqueous solvent through the ion exchange resin in addition to drying under reduced pressure to remove the moisture are known (Patent Document 1). However, the moisture content of the ion exchange resin cannot be sufficiently reduced only by drying under reduced pressure. In addition, the method of passing a pretreatment nonaqueous solvent in addition to drying under reduced pressure has a problem that a large amount of the pretreatment nonaqueous solvent, which is several tens to several hundreds times the amount of the ion exchange resin, is required.

[0004] Therefore, as described in Patent Document 2, a method has been proposed in which a stock solution tank for storing a pretreatment nonaqueous solvent, an ion exchange resin container containing an ion exchange resin, and a moisture removal device for removing moisture from the pretreatment nonaqueous solvent are combined, and the pretreatment nonaqueous solvent is circulated using a liquid delivery means such as a pump, thereby reducing the moisture content of the ion exchange resin with a small amount of pretreatment nonaqueous solvent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2000-505042 [Patent Document 2] JP 2020-121261 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method described in Patent Document 2, a pretreatment nonaqueous solvent having a composition similar to that of the nonaqueous solvent to be purified is preferably used as the pretreatment nonaqueous solvent, and therefore, it is necessary to change the pretreatment nonaqueous solvent every time the nonaqueous solvent to be purified is changed.

[0007] Therefore, an object of the present invention is to provide a method and apparatus for purifying a non-aqueous solvent using an ion exchange resin with a reduced water content in a simple and economical manner, without requiring a variety of non-aqueous solvents for pretreatment. [Means for solving the problem]

[0008] In view of the above-mentioned object, the inventors have conducted intensive research and have found that the above-mentioned problem can be solved by replacing and removing water in an ion exchange resin with a pretreatment nonaqueous solvent which has a high affinity for water and a relative dielectric constant of 15 or more at 25°C, and then contacting the ion exchange resin with a nonaqueous solvent to be purified which has a component identity with the pretreatment nonaqueous solvent of 85% by mass or less, thereby completing the present invention.

[0009] That is, the present invention provides a method for purifying a non-aqueous solvent using an ion exchange resin, the method comprising: a pretreatment step of contacting an ion exchange resin with a pretreatment non-aqueous solvent having a relative dielectric constant of 15 or more at 25° C.; and a purification step of contacting the ion exchange resin after the pretreatment step with a non-aqueous solvent to be purified, wherein the component match rate between the pretreatment non-aqueous solvent and the non-aqueous solvent to be purified is 85% by mass or less. The non-aqueous solvent constituting the pretreatment non-aqueous solvent is selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, acetone, 2-butanone, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. The method for purifying a non-aqueous solvent is characterized by:

[0010] The present invention also relates to an apparatus for purifying a non-aqueous solvent using an ion exchange resin, the apparatus comprising: a pretreatment means for contacting an ion exchange resin with a pretreatment non-aqueous solvent having a relative dielectric constant of 15 or more at 25° C.; and a purification means for contacting the ion exchange resin that has been contacted with the pretreatment non-aqueous solvent with a non-aqueous solvent to be purified, wherein the component match rate between the pretreatment non-aqueous solvent and the non-aqueous solvent to be purified is 85% by mass or less. The non-aqueous solvent constituting the pretreatment non-aqueous solvent is selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, acetone, 2-butanone, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. The present invention relates to a purification apparatus for a non-aqueous solvent. Effect of the Invention

[0011] According to the present invention, it is possible to provide a method and apparatus for purifying a nonaqueous solvent using an ion exchange resin having a reduced water content in a simple and economical manner without requiring a variety of pretreatment nonaqueous solvents. Furthermore, according to the present invention, even when a pretreatment nonaqueous solvent having a low component match rate with the nonaqueous solvent to be purified is used, it is possible to suppress water elution from the ion exchange resin during nonaqueous solvent purification. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a configuration of a pretreatment device according to an embodiment of the present invention; [Diagram 2] 1 is a schematic diagram showing a configuration of a purification device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Method of purifying non-aqueous solvent> The method for purifying a non-aqueous solvent according to the present invention is a method for purifying a non-aqueous solvent using an ion exchange resin, and includes a pretreatment step of contacting the ion exchange resin with a pretreatment non-aqueous solvent having a relative dielectric constant of 15 or more at 25° C., and a purification step of contacting the ion exchange resin after the pretreatment step with the non-aqueous solvent to be purified. In addition, the component match rate between the pretreatment non-aqueous solvent and the non-aqueous solvent to be purified is 85% by mass or less. The present invention will be described in detail below.

[0014] [Pretreatment process] The pretreatment step is a step of contacting an ion exchange resin with a pretreatment nonaqueous solvent having a relative dielectric constant of 15 or more at 25°C. By carrying out the pretreatment step, the moisture contained in the ion exchange resin can be efficiently reduced. As a result, when the ion exchange resin is used for purifying the nonaqueous solvent to be purified, it is possible to suppress the elution of moisture from the resin into the nonaqueous solvent to be purified. The ion exchange resin may be dried by a known method such as drying under reduced pressure before being used in the pretreatment step.

[0015] (Ion exchange resin) The ion exchange resin used in the present invention is not particularly limited, but is preferably an organic polymer-based ion exchange resin having an organic polymer as a host. Examples of the host organic polymer include styrene-based resins and acrylic-based resins.

[0016] In this specification, the term "styrene-based resin" refers to a resin containing 50% by mass or more of structural units derived from styrene or a styrene derivative, either homopolymerized or copolymerized with styrene or a styrene derivative. Examples of styrene derivatives include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene.

[0017] The styrene-based resin may be a copolymer with other copolymerizable vinyl monomers, so long as it is mainly composed of a homopolymer or copolymer of styrene or a styrene derivative. Examples of such vinyl monomers include at least one selected from divinylbenzenes such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene; polyfunctional monomers such as alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and polyethylene glycol di(meth)acrylate; (meth)acrylonitrile, methyl (meth)acrylate, and the like. Among these, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylates having an ethylene polymerization number of 4 to 16, and divinylbenzene are preferred, divinylbenzene and ethylene glycol di(meth)acrylate are more preferred, and divinylbenzene is particularly preferred.

[0018] In addition, in this specification, "acrylic resin" refers to a resin which is homopolymerized or copolymerized with one or more selected from acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters, and which contains 50 mass% or more of structural units selected from structural units derived from acrylic acid, structural units derived from methacrylic acid, structural units derived from acrylic acid esters, and structural units derived from methacrylic acid esters.

[0019] Examples of the acrylic resin include at least one selected from homopolymers of acrylic acid, homopolymers of methacrylic acid, homopolymers of acrylic esters, homopolymers of methacrylic esters, copolymers of acrylic acid and other monomers (e.g., acrylic esters, methacrylic acid, methacrylic esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), copolymers of methacrylic acid and other monomers (e.g., acrylic acid, acrylic esters, methacrylic esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), copolymers of acrylic esters and other monomers (e.g., acrylic acid, methacrylic acid, methacrylic esters, α-olefins (e.g., ethylene, divinylbenzene, etc.)), and copolymers of methacrylic esters and other monomers (e.g., acrylic acid, acrylic esters, methacrylic acid, α-olefins (e.g., ethylene, divinylbenzene, etc.)). Among these, methacrylic acid-divinylbenzene copolymers or acrylic acid-divinylbenzene copolymers are preferred.

[0020] The acrylic acid ester is preferably an alkyl acrylate, more preferably a linear or branched alkyl ester of acrylic acid, and even more preferably a linear alkyl ester of acrylic acid. The alkyl ester moiety preferably has 1 to 4 carbon atoms, and the acrylic acid ester is particularly preferably methyl acrylate or ethyl acrylate.

[0021] The methacrylic acid ester is preferably a methacrylic acid alkyl ester, more preferably a linear or branched alkyl ester of methacrylic acid, and even more preferably a linear alkyl ester of methacrylic acid. The number of carbon atoms of the alkyl group contained in the alkyl ester moiety is preferably 1 to 4, and the methacrylic acid alkyl ester is particularly preferably methyl methacrylate or ethyl methacrylate.

[0022] The ion exchange resin may be either a cation exchange resin or an anion exchange resin, or may be a chelating resin. The ion exchange resin may be either a transparent gel type having small pores, a macrolitercular type (MR type) having large pores, or a macroporous type (also called a porous type or high-porous type).

[0023] Examples of the cation exchange resin include a strongly acidic cation exchange resin having a sulfonic acid group and a weakly acidic cation exchange resin having a carboxylic acid group. The ion form of the cation exchange resin is not limited, but from the viewpoint of removing impurities such as metals, a hydrogen ion form (H form) is preferable. Examples of the cation exchange resin include Amberlite (registered trademark) IRN99H (gel-type strongly acidic cation exchange resin, trade name, manufactured by DuPont), Amberjet (registered trademark) 1060H (gel-type strongly acidic cation exchange resin, trade name, manufactured by Organo Corporation), Orlite (registered trademark) DS-1 (gel-type strongly acidic cation exchange resin, trade name, manufactured by Organo Corporation), and Orlite (registered trademark) DS-4 (macroporous type strongly acidic cation exchange resin, trade name, manufactured by Organo Corporation).

[0024] Examples of anion exchange resins include strongly basic anion exchange resins having quaternary ammonium bases and weakly basic anion exchange resins having primary to tertiary amino groups. The ion form of the strongly basic anion exchange resin is not limited, but from the viewpoint of removing impurities such as metals, hydroxide ion form (OH form), carbonate form or bicarbonate form is generally used. The ion form of the weakly basic anion exchange resin is not limited, but from the viewpoint of removing impurities such as metals, free base form is generally used. Examples of anion exchange resins include Orlite (registered trademark) DS-2 (gel type strongly basic anion exchange resin, trade name, manufactured by Organo Corporation), DS-6 (MR type weakly basic anion exchange resin, trade name, manufactured by Organo Corporation), and Diaion (registered trademark) WA30 (high-porous type weakly basic anion exchange resin, trade name, manufactured by Mitsubishi Chemical Corporation).

[0025] The chelating resin is not particularly limited, but examples thereof include Orlite (registered trademark) DS-21 and DS-22 (both are macroporous chelating resins, trade names, manufactured by Organo Corporation).

[0026] (Non-aqueous solvent for pretreatment) The pretreatment nonaqueous solvent has a relative dielectric constant of 15 or more at 25° C. The relative dielectric constant of the pretreatment nonaqueous solvent at 25° C. is preferably 18 or more. The pretreatment nonaqueous solvent is not limited as long as it has a relative dielectric constant of 15 or more at 25° C. and is soluble in water. The pretreatment nonaqueous solvent may be composed of two or more nonaqueous solvents. In this case, it is sufficient that the mixed nonaqueous solvent obtained by mixing two or more nonaqueous solvents has a relative dielectric constant of 15 or more at 25° C. and is soluble in water. Examples of non-aqueous solvents constituting the pretreatment non-aqueous solvent include carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), etc., ketones such as acetone and 2-butanone, alcohols such as methanol, ethanol, isopropyl alcohol, etc., glycols such as ethylene glycol and propylene glycol, propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), etc. These non-aqueous solvents may be used alone or in combination of two or more.

[0027] In this specification, the dielectric constant of a mixed nonaqueous solvent means a value calculated based on the dielectric constant of each nonaqueous solvent contained in the mixed nonaqueous solvent and its volume ratio. A ) and non-aqueous solvent B (relative dielectric constant ε B The relative dielectric constant ε of a mixed nonaqueous solvent (volume ratio α:β, α+β=100) composed of the above is calculated by the following formula. ε = (ε A ×(α / 100))+(ε B ×(β / 100))

[0028] There are no restrictions on the relationship between the dielectric constants of the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified, and as long as the dielectric constant is 15 or more, the pretreatment nonaqueous solvent can be one having a smaller dielectric constant than the nonaqueous solvent to be purified, one having a larger dielectric constant than the nonaqueous solvent to be purified, or one having the same dielectric constant as the nonaqueous solvent to be purified.

[0029] In the present invention, the component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified described below is 85% by mass or less. Here, the component matching rate is a value (mass%) calculated by comparing the mass proportions of each component contained in the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified, and integrating the mass proportions of the one with the smaller mass proportion (component matching rate of each component). For example, if there is a component that is contained only in one of the nonaqueous solvents, the component matching rate of the component is "0% by mass", and this is integrated with the component matching rate of the other component to calculate the component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified. That is, in the present invention, the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified do not need to be the same solvent, and the above-mentioned effect of the present invention can be exhibited even when the component matching rate between the two is low or when the two are completely different solvents (the component matching rate between the two is 0% by mass). Therefore, according to the present invention, it is possible to reliably reduce the moisture content of the ion exchange resin without using a pretreatment nonaqueous solvent having a high component match rate with the nonaqueous solvent to be purified, and it is possible to reduce the amount of the nonaqueous solvent to be purified that contains a lot of moisture immediately after purification and is discarded in the purification step described below. It is also possible to save the effort of changing the pretreatment nonaqueous solvent according to the type of the nonaqueous solvent to be purified.

[0030] The water concentration in the pretreatment nonaqueous solvent is preferably 10 ppm or less. If the water concentration in the pretreatment nonaqueous solvent is 10 ppm or less, it is possible to prevent water contamination of the resin by the pretreatment nonaqueous solvent in the pretreatment step. Examples of pretreatment nonaqueous solvents having a water concentration of 10 ppm or less include pretreatment nonaqueous solvents of a grade for lithium ion batteries. The water concentration (ppm) is a value measured by the Karl Fischer method using, for example, a Karl Fischer volumetric moisture meter (product name: Aquacounter AQ-2200, manufactured by Hiranuma Sangyo Co., Ltd.). ppm represents the mass ratio of water to the target nonaqueous solvent.

[0031] The method for contacting the ion exchange resin with the pretreatment nonaqueous solvent is not particularly limited, and examples thereof include a batch treatment method and a continuous liquid passing treatment method using a column. Of these, the continuous liquid passing treatment method is preferred from the viewpoints of operability and efficiency.

[0032] In the continuous liquid passing treatment method, the ion exchange resin is packed in a purification tower such as a column. The height of the resin packed bed in the purification tower may be, for example, 100 to 1000 mm, depending on the height of the purification tower. Next, the pretreatment nonaqueous solvent is added at a rate of, for example, SV (space velocity, h -1 At a bed volume of 0.5 to 50, 2 to 200 BV is passed through the ion exchange resin. Here, BV (Bed volume) represents the multiple of the amount of non-aqueous solvent passed through relative to the amount of resin. The direction of the liquid passing may be either downward or upward. By passing the liquid through the ion exchange resin in this manner, the water contained in the ion exchange resin is successively replaced with the pretreatment non-aqueous solvent and removed.

[0033] Next, the batch processing method will be described. First, the ion exchange resin is filled in a reaction tank equipped with a stirrer. Next, the pretreatment nonaqueous solvent is filled in the reaction tank. The volume ratio is not particularly limited, but 2 to 200 parts of nonaqueous solvent per 1 part of resin is preferable. After that, it is preferable to leave it for about 0.1 to 16 hours, for example, in order to make the resin and the nonaqueous solvent compatible. After leaving it, the stirrer is operated to mix the resin and the nonaqueous solvent uniformly. The stirring speed and stirring time may be appropriately determined depending on the size of the reaction tank, the amount of processing, etc. After the stirring is completed, filtration or the like is performed to separate the resin from the pretreatment nonaqueous solvent, thereby obtaining a resin from which moisture has been removed.

[0034] The ion exchange resin after the pretreatment step can be stored in a state immersed in the pretreatment nonaqueous solvent used in the pretreatment step until it is used in the purification of the nonaqueous solvent to be purified. In that case, when used in the purification step, the resin and the pretreatment nonaqueous solvent can be separated and used in the purification of the nonaqueous solvent to be purified. In addition, the ion exchange resin after the pretreatment step can be drained with an inert gas such as nitrogen to remove the pretreatment nonaqueous solvent, and then stored in a sealed state. In this case, the stored ion exchange resin can be used in the purification step as it is.

[0035] [Moisture removal process] The pretreatment nonaqueous solvent containing a large amount of water after contact with the ion exchange resin in the pretreatment step is usually discarded. However, if a water removal step for removing water from the pretreatment nonaqueous solvent after use in the pretreatment step is carried out, the pretreatment nonaqueous solvent after the water removal step can be reused as the pretreatment nonaqueous solvent to be used in the pretreatment step, and the amount of nonaqueous solvent used can be further reduced. That is, the purification method according to the present invention may have a water removal step in which the pretreatment nonaqueous solvent after contact with the ion exchange resin in the pretreatment step is brought into contact with a water removal device.

[0036] In addition, in order to reuse the pretreatment nonaqueous solvent after the contact with the ion exchange resin and the moisture removing device in the moisture removing step as the pretreatment nonaqueous solvent to be used in the pretreatment step, it is also possible to carry out the pretreatment step while circulating the pretreatment nonaqueous solvent. That is, the purification method according to the present invention may include at least a tank for storing the pretreatment nonaqueous solvent, an ion exchange resin container filled with an ion exchange resin, and a moisture removing device for removing moisture from the pretreatment nonaqueous solvent, and may be a method in which the pretreatment nonaqueous solvent is contacted from the tank to the ion exchange resin container and the moisture removing device in that order, and then the pretreatment nonaqueous solvent is returned to the tank while circulating the pretreatment nonaqueous solvent. This makes it possible to efficiently reuse the pretreatment nonaqueous solvent used for removing moisture with the ion exchange resin. The pretreatment nonaqueous solvent can be circulated, for example, using a circulation liquid sending pipe.

[0037] The moisture removal device may include, for example, a device containing a moisture adsorbent such as zeolite. The zeolite is not particularly limited as long as it can adsorb moisture in a non-aqueous solvent, and may include one or more types of crystalline zeolite selected from A-type, Y-type, X-type, chabazite, ferrierite, ZSM-5, clinoptilolite, and the like.

[0038] The crystalline zeolite preferably has a Si / Al molar ratio of 1 to 5. By having the Si / Al molar ratio within the above range, the crystalline zeolite is structurally stable and has a suitable cation content, and can adsorb and remove moisture appropriately. The crystalline zeolite may have cations exchanged with lithium ions, calcium ions, or the like, or may not be exchanged. The crystalline zeolite preferably has a pore diameter of 3 Å to 10 Å, more preferably 3 Å to 6 Å, and even more preferably 3 Å to 5 Å. By having the pore diameter within the above range, moisture in a non-aqueous solvent can be adsorbed and removed appropriately. The pore diameter means a theoretical value estimated from the crystal structure and the cation species held.

[0039] The form of the zeolite packed in the moisture remover is not particularly limited as long as the non-aqueous solvent and the zeolite can be in contact with each other. The moisture remover may be, for example, a column or tank packed with zeolite through which the non-aqueous solvent can pass. The moisture remover may also be equipped with a pump for passing the non-aqueous solvent. The method of contacting the pre-treatment non-aqueous solvent with the moisture remover may be the same as the above-mentioned method of contacting the ion exchange resin with the pre-treatment non-aqueous solvent. However, it is preferable to arrange the moisture remover so that the pre-treatment non-aqueous solvent passes through the zeolite packed in the moisture remover in an upward flow. The speed at which the non-aqueous solvent passes through the zeolite may be appropriately selected from the speed at which the moisture in the non-aqueous solvent can be removed.

[0040] [Refining process] The purification step is a step of purifying the nonaqueous solvent to be purified by contacting the ion exchange resin, the moisture content of which has been reduced after the pretreatment step, with the nonaqueous solvent to be purified.

[0041] (Non-aqueous solvent to be purified) The non-aqueous solvent to be purified is, for example, a chemical solution and a solvent used in the battery industry or the electronics industry. Specific examples of the non-aqueous solvent to be purified include carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC), ketones such as acetone and 2-butanone, alcohols such as methanol, ethanol, and isopropyl alcohol, glycols such as ethylene glycol and propylene glycol, propylene glycol monomethyl ether (PGME), and propylene glycol monomethyl ether acetate (PGMEA). These non-aqueous solvents may be used alone or in combination of two or more. In addition, electrolytes, various additives, and other chemical solutions may be dissolved in these chemical solutions or solvents. Examples of electrolytes include LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiAlCl4, LiCF3SO3, LiN(SO2F)2, LiN(SO2CF3)2, etc. Among these, the refining method according to the present invention is particularly preferably used for refining electrolytes for lithium ion batteries.

[0042] The non-aqueous solvent to be purified preferably contains two or more components. The components referred to here mean components contained in the non-aqueous solvent to be purified (100% by mass) at 5% by mass or more. In other words, the non-aqueous solvent to be purified is preferably a mixed non-aqueous solvent containing two or more components contained in the non-aqueous solvent to be purified at 5% by mass or more. The components include the non-aqueous solvents and electrolytes exemplified above. For example, propylene carbonate to which 5% by mass or more of an electrolyte has been added (the total of the electrolyte and propylene carbonate is 100% by mass) is a non-aqueous solvent to be purified containing two components.

[0043] The method for contacting the ion exchange resin after the pretreatment step with the nonaqueous solvent to be purified may be the same as the above-mentioned method for contacting the ion exchange resin with the pretreatment nonaqueous solvent.

[0044] In addition, before the non-aqueous solvent to be purified is brought into contact with the ion exchange resin to perform actual purification, a treatment may be performed to replace the pre-treatment non-aqueous solvent with the non-aqueous solvent to be purified, if necessary. In this case, the non-aqueous solvent to be purified can be replaced with the pre-treatment non-aqueous solvent by passing the non-aqueous solvent to be purified, usually at 1 to 20 BV. Since the non-aqueous solvent to be purified and the non-aqueous solvent to be purified are usually easily mixed, it is considered that most of the pre-treatment non-aqueous solvent is pushed out and removed by the solvent replacement with the non-aqueous solvent to be purified by performing this treatment. However, if the small amount of the pre-treatment non-aqueous solvent remaining becomes an impurity for the non-aqueous solvent to be purified, it is desirable to analyze the concentration of the pre-treatment non-aqueous solvent in the non-aqueous solvent to be purified as appropriate, and pass the non-aqueous solvent to be purified until the concentration of the pre-treatment non-aqueous solvent is reduced to a target concentration or less.

[0045] <Non-aqueous solvent purification equipment> The nonaqueous solvent purification apparatus according to the present invention is an apparatus for purifying a nonaqueous solvent using an ion exchange resin, and includes a pretreatment means for contacting the ion exchange resin with a pretreatment nonaqueous solvent having a relative dielectric constant of 15 or more at 25° C., and a purification means for contacting the ion exchange resin, which has been contacted with the pretreatment nonaqueous solvent, with a nonaqueous solvent to be purified. The component match rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified is 85 mass % or less. Details of the pretreatment means and purification means are the same as those described in the pretreatment step and purification step, respectively, of the method for purifying a nonaqueous solvent described above.

[0046] The purification apparatus according to the present invention may also have a moisture removing means for contacting the pretreatment nonaqueous solvent after contacting the ion exchange resin in the pretreatment means with a moisture removing device. Furthermore, in order to reuse the pretreatment nonaqueous solvent after contacting the ion exchange resin and the moisture removing device in that order as the pretreatment nonaqueous solvent to be used in the pretreatment means, it is also possible to carry out the pretreatment means while circulating the pretreatment nonaqueous solvent. That is, the purification apparatus according to the present invention may have at least a tank for storing the pretreatment nonaqueous solvent, an ion exchange resin container filled with an ion exchange resin, and a moisture removing device for removing moisture from the pretreatment nonaqueous solvent, and may also have a circulation liquid sending means for returning the pretreatment nonaqueous solvent to the tank after contacting the pretreatment nonaqueous solvent with the ion exchange resin container and the moisture removing device in that order from the tank. Details of the moisture removing device are as described in the moisture removing step related to the purification method of a nonaqueous solvent. An example of the circulation liquid sending means is a circulation liquid sending tube.

[0047] FIG. 1 is a schematic diagram showing the configuration of a pretreatment device as a pretreatment means according to one embodiment of the present invention. FIG. 1 shows an example of a purification device according to the present invention in which the pretreatment device is provided separately from a purification device (FIG. 2) as a purification means. However, for example, the pretreatment device shown in FIG. 1 and the purification device shown in FIG. 2 can be combined to form a purification device according to the present invention. In that case, a common ion exchange resin container may be used. The pretreatment device shown in FIG. 1 has a tank 1 for storing a pretreatment nonaqueous solvent, an ion exchange resin container 2 filled with an ion exchange resin, a moisture removal device 3 containing zeolite, and a circulation liquid sending pipe L as a circulation liquid sending means. In the pretreatment device, the pretreatment nonaqueous solvent is passed from the tank 1 to the ion exchange resin container and the moisture removal device in this order using a pump P, and then the passed pretreatment nonaqueous solvent is returned to the tank by the circulation liquid sending pipe L. It is preferable that the circulation liquid sending pipe L is arranged so that the pretreatment nonaqueous solvent flowing in the circulation liquid sending pipe L flows upward with respect to the zeolite filled in the moisture removal device 3, as shown in FIG. 1. Before the pretreatment, the ion exchange resin may be washed with an acid / alkali aqueous solution, pure water, etc. When washing with an acid / alkali aqueous solution, etc., a resistivity meter or conductivity meter is provided at the outlet of the ion exchange resin container to check the resistivity value or conductivity value, while taking care not to mix the acid / alkali aqueous solution, etc. with the pretreatment nonaqueous solvent.

[0048] FIG. 2 is a schematic diagram showing the configuration of a purification device as a purification means according to one embodiment of the present invention. The purification device shown in FIG. 2 has a tank 4 for storing the non-aqueous solvent to be purified before purification, an ion exchange resin container 5 filled with an ion exchange resin after removing moisture using the pretreatment device, and a tank 6 for storing the non-aqueous solvent to be purified after purification. In the purification device, the non-aqueous solvent to be purified is passed from the tank 4 to the ion exchange resin container 5 using a pump P, and the purified non-aqueous solvent to be purified is recovered in the tank 6. The non-aqueous solvent to be purified can be passed through the ion exchange resin in an upward or downward flow as appropriate. When the true density of the ion exchange resin is smaller than the density of the non-aqueous solvent to be purified, it is preferable to pass the non-aqueous solvent through the ion exchange resin in an upward flow, and when the true density of the ion exchange resin is larger than the density of the non-aqueous solvent to be purified, it is preferable to pass the non-aqueous solvent in a downward flow. The pretreatment of the ion exchange resin and the purification of the non-aqueous solvent to be purified do not necessarily have to be performed consecutively. However, if they are not performed consecutively, it is necessary to store the ion exchange resin after the pretreatment in a sealed state so that it does not come into contact with moisture or metal impurities. EXAMPLES

[0049] The effects of the present invention will be described below with reference to examples, but these are merely illustrative and do not limit the present invention.

[0050] [Example 1] The ion exchange resin pretreatment device shown in FIG. 1 was used to perform pretreatment of the ion exchange resin, and then the nonaqueous solvent to be purified was purified using the purification device shown in FIG. As the nonaqueous solvent for pretreatment, a nonaqueous solvent (water concentration <10 ppm) in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 2:1 (mass ratio of 72:28) was used. The non-aqueous solvent to be purified was a 1:1 volumetric mixture of EC and dimethyl carbonate (DMC), and an electrolyte solution was used in which LiPF6 was dissolved at 1 mol / L in the non-aqueous solvent (LiPF6:EC:DMC (mass ratio) = 11:49:40, water concentration <10 ppm). Other conditions are as follows:

[0051] (Ion exchange resin container) Teflon (registered trademark) column (inner diameter: 26 mm, height: 200 mm) (moisture removal device) Teflon (registered trademark) column (inner diameter: 26 mm, height: 200 mm) (Filler) Ion exchange resin: Dimethylamine group, styrene type, MR type, filling volume 40 mL Zeolite: pore size 4Å, packing volume 80mL (Pretreatment conditions) Flow rate of pretreatment non-aqueous solvent through ion exchange resin: 10 (L / L-resin) / h Flow rate of non-aqueous solvent for pretreatment through zeolite: 5 (L / L-zeolite) / h Flow time: 17 hours (Purification conditions) Flow rate of non-aqueous solvent to be purified through ion exchange resin: 10 (L / L-resin) / h

[0052] Under the above conditions, the ion exchange resin was pretreated and the nonaqueous solvent to be purified was purified. After 2 BV of the nonaqueous solvent to be purified was passed through the ion exchange resin, the water concentration in the nonaqueous solvent to be purified at the column outlet was measured. The water concentration (ppm by mass) was measured by the Karl Fischer method using a Karl Fischer volumetric moisture meter (product name: Aquacounter AQ-2200, manufactured by Hiranuma Sangyo Co., Ltd.). The ppm indicates the mass ratio of water to the nonaqueous solvent to be purified. Table 1 shows the composition and dielectric constant of the pretreatment nonaqueous solvent, the component match rate (mass%) between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified, and the water concentration (ppm by mass) in the nonaqueous solvent to be purified 2 BV after the start of the pass. The dielectric constant of the mixed solvent is a value calculated based on the dielectric constant of each solvent contained in the mixed solvent and its volume ratio.

[0053] [Example 2] Except for using a nonaqueous solvent (water concentration <10 ppm) in which EC and EMC were mixed at a volume ratio of 1:3 (mass ratio of 30:70) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0054] [Example 3] Except for using a nonaqueous solvent (water concentration <10 ppm) in which EC and EMC were mixed at a volume ratio of 1:5 (mass ratio of 21:79) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0055] [Example 4] Except for using a nonaqueous solvent (water concentration <10 ppm) in which EC and dimethyl carbonate (DMC) were mixed at a volume ratio of 2:1 (mass ratio of 71:29) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0056] [Example 5] Except for using propylene carbonate (PC, water concentration <10 ppm) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0057] [Example 6] Except for using 2-butanone (water concentration <10 ppm) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0058] [Comparative Example 1] Except for using a nonaqueous solvent (water concentration <10 ppm) in which EC and EMC were mixed at a volume ratio of 1:9 (mass ratio of 13:87) as the pretreatment nonaqueous solvent, the pretreatment of the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0059] [Comparative Example 2] Except for using DMC (water concentration <10 ppm) as the pretreatment nonaqueous solvent, the pretreatment with the ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0060] [Comparative Example 3] Except for using EMC (water concentration <10 ppm) as the pretreatment nonaqueous solvent, the pretreatment with ion exchange resin and the purification of the nonaqueous solvent to be purified were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0061] [Table 1]

[0062] The component matching rate (mass%) between the nonaqueous solvent to be purified and the nonaqueous solvent for pretreatment was calculated by comparing the mass proportions of each component contained in each nonaqueous solvent and integrating the mass proportions of the lesser mass proportion (component matching rate of each component). As an example, a method for calculating the component matching rate between the nonaqueous solvent to be purified and the nonaqueous solvent for pretreatment in Example 1 is shown in Table 2. As shown in Table 2, when an EC / EMC mixed solvent (volume ratio 2:1, mass ratio 72:28) was used as the nonaqueous solvent for pretreatment and an electrolyte solution of LiPF6:EC:DMC (mass ratio 11:49:40) was used as the nonaqueous solvent to be purified, the integrated value of the component matching rate for each component was 49 mass%.

[0063] [Table 2]

[0064] As shown in Table 1, when the non-aqueous solvent to be purified is purified using an ion exchange resin pretreated with a pretreatment non-aqueous solvent having a relative dielectric constant of 15 or more at 25°C as in Examples 1 to 6, almost no moisture derived from the ion exchange resin is dissolved in the non-aqueous solvent to be purified after 2 BV from the start of liquid passing. That is, it is understood that the moisture in the ion exchange resin is efficiently removed in the pretreatment step. On the other hand, when the non-aqueous solvent to be purified is purified using an ion exchange resin pretreated with a pretreatment non-aqueous solvent having a relative dielectric constant of less than 15 as in Comparative Examples 1 to 3, it is understood that a large amount of moisture derived from the ion exchange resin is dissolved in the non-aqueous solvent to be purified after 2 BV from the start of liquid passing.

[0065] In addition, as in the examples, if the relative dielectric constant of the pretreatment nonaqueous solvent is 15 or more, even if the component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified is low, it does not affect the water elution from the ion exchange resin in the purification process. On the other hand, as in the comparative example, when the relative dielectric constant of the pretreatment nonaqueous solvent is less than 15, it was found that the amount of water eluted from the ion exchange resin in the purification process is greatly affected by the component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified. In particular, when comparing Comparative Example 2 and Comparative Example 3, it was found that the lower the component matching rate, the more water eluted from the ion exchange resin and the amount of the nonaqueous solvent to be discarded increases. That is, according to the present invention, it is possible to reliably reduce the water content of the ion exchange resin even without using a pretreatment nonaqueous solvent with a high component matching rate with the nonaqueous solvent to be purified, and the amount of the nonaqueous solvent to be discarded can be reduced. [Explanation of symbols]

[0066] 1: Tank (non-aqueous solvent for pretreatment) 2: Ion exchange resin container 3: Moisture removal device 4: Tank (non-aqueous solvent to be purified before purification) 5: Ion exchange resin container 6: Tank (non-aqueous solvent to be purified after purification) L: Circulation liquid pipe P: Pump

Claims

1. A method for purifying a non-aqueous solvent using an ion exchange resin, comprising the steps of: a pretreatment step of contacting an ion exchange resin with a pretreatment nonaqueous solvent having a relative dielectric constant of 15 or more at 25°C; a purification step of contacting the ion exchange resin after the pretreatment step with a nonaqueous solvent to be purified; a component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified is 85% by mass or less, and the nonaqueous solvent constituting the pretreatment nonaqueous solvent is selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, acetone, 2-butanone, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.

2. The method for purifying a non-aqueous solvent according to claim 1 , wherein the non-aqueous solvent to be purified is a mixed non-aqueous solvent containing two or more components each of which is contained in the non-aqueous solvent at 5% by mass or more.

3. 3. The method for purifying a non-aqueous solvent according to claim 1, further comprising a moisture removing step of contacting the pretreatment non-aqueous solvent after contact with the ion exchange resin in the pretreatment step with a moisture remover.

4. An apparatus for purifying a non-aqueous solvent using an ion exchange resin, A pretreatment means for contacting an ion exchange resin with a pretreatment nonaqueous solvent having a relative dielectric constant of 15 or more at 25° C.; a purification means for contacting the ion exchange resin that has been in contact with the pretreatment nonaqueous solvent with a nonaqueous solvent to be purified; a component matching rate between the pretreatment nonaqueous solvent and the nonaqueous solvent to be purified is 85 mass % or less, and the nonaqueous solvent constituting the pretreatment nonaqueous solvent is selected from ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, acetone, 2-butanone, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate.

5. The apparatus for purifying a nonaqueous solvent according to claim 4 , wherein the nonaqueous solvent to be purified is a mixed nonaqueous solvent containing two or more components each of which is contained in the nonaqueous solvent to be purified at 5% by mass or more.

6. 6. The apparatus for purifying a nonaqueous solvent according to claim 4, further comprising a moisture removing means for contacting the pretreatment nonaqueous solvent after contact with the ion exchange resin in the pretreatment means with a moisture removing device.

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