Operating method of a liquid purification apparatus

Abstract

To reduce the amount of a non-aqueous solvent used in dehydration treatment of a monolithic organic porous ion exchanger.SOLUTION: The operation method of a liquid purification device 10 having a monolithic organic porous ion exchanger as purification means 11 for purifying a non-aqueous solvent includes the steps of: passing a non-aqueous solvent to be purified or a non-aqueous solvent different from the non-aqueous solvent to be purified through the purification means 11 as a dehydration treatment liquid and removing water contained in the purification means 11 by eluting it into the dehydration treatment liquid; and after removing the water contained in the purification means 11, passing the non-aqueous solvent to be purified through the purification means 11 and removing ionic components contained in the non-aqueous solvent to be purified, by the purification means 11. The step of passing the dehydration treatment liquid includes passing the dehydration treatment liquid through the purification means 11 at a flow rate lower than the flow rate when passing the non-aqueous solvent to be purified through the purification means 11.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for operating a liquid purification apparatus. [Background technology]

[0002] Highly purified non-aqueous solvents are used in the manufacturing processes of semiconductor devices and lithium-ion batteries. One known method for purifying non-aqueous solvents involves passing the non-aqueous solvent to be purified (liquid to be purified) through an ion exchanger such as an ion exchange resin or a monolithic organic porous ion exchanger to remove impurities (ionic components such as metal ions) from the liquid (see, for example, Patent Documents 1 and 2). However, this method carries the risk that water contained in the ion exchanger may dissolve into the liquid to be purified, which may prevent it from meeting the recent demand for high purity of non-aqueous solvents. Therefore, in the purification of non-aqueous solvents using the above method, a dehydration treatment is also performed prior to the purification, in which a non-aqueous solvent for dehydration treatment (dehydration treatment liquid) is passed through the ion exchanger to dissolve and remove its contained water (see, for example, Patent Document 3).

[0003] Incidentally, the dehydration solution used in the dehydration treatment of ion exchangers is sometimes reused after the water has been removed, but in most cases it is discarded, so it is preferable to use as little as possible. In response to this, Patent Document 3 proposes a method to reduce the amount of dehydration solution used by reducing the particle size of the ion exchange resin in order to make it easier to remove water near the center of the ion exchange resin. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2015-521101 [Patent Document 2] Japanese Patent Publication No. 2019-195763 [Patent Document 3] Japanese Patent Publication No. 2021-109833 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the methods described above are applied to ion exchange resins, and no methods have been proposed to date for applying them to monolithic organic porous ion exchangers, which can achieve both high-flow-rate purification and impurity removal performance compared to ion exchange resins.

[0006] Therefore, the object of the present invention is to provide a method for operating a liquid purification apparatus that reduces the amount of non-aqueous solvent used in the dehydration treatment of monolithic organic porous ion exchangers. [Means for solving the problem]

[0007] To achieve the above-mentioned objectives, the present invention provides a method for operating a liquid purification apparatus having a monolithic organic porous ion exchanger as a purification means for purifying a non-aqueous solvent, comprising the steps of: passing the non-aqueous solvent to be purified or a non-aqueous solvent other than the non-aqueous solvent to be purified through the purification means as a dehydration liquid, and removing the water contained in the purification means by dissolving it into the dehydration liquid; and, after removing the water contained in the purification means, passing the non-aqueous solvent to be purified through the purification means, and removing the ionic components contained in the purified non-aqueous solvent by the purification means, wherein the dehydration liquid Purification method Allow fluid to pass through The flow rate at the end , After removing the water contained in the purification method Less than the flow rate when passing the non-aqueous solvent to be purified through the purification means. Make .

[0008] This method of operating the liquid purification apparatus allows for sufficient and reliable contact between the monolithic organic porous ion exchange medium, which has a large specific surface area, and the dewatering liquid during its passage. As a result, water contained in the monolithic organic porous ion exchange medium is more easily removed, and the amount of dewatering liquid required for this purpose can be reduced. [Effects of the Invention]

[0009] As described above, according to the present invention, the amount of non-aqueous solvent used in the dehydration treatment of monolithic organic porous ion exchange bodies can be reduced. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a liquid purification apparatus according to one embodiment of the present invention. [Figure 2] This graph shows the time-dependent changes in water concentration in the dewatered solution after passing it through a monolithic organic porous ion exchanger under conditions A1 to A3. [Figure 3] This graph shows the time-dependent changes in the water concentration in the dewatered solution after passing it through a monolithic organic porous ion exchanger under conditions B1 to B3. [Figure 4] This graph shows the time-dependent changes in water concentration in the dewatered solution after passing it through a monolithic organic porous ion exchanger under conditions C1 to C3. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings.

[0012] Figure 1 is a schematic diagram of a liquid purification apparatus according to one embodiment of the present invention.

[0013] The liquid purification device 10 purifies a non-aqueous solvent by removing impurities (ionic components such as metal ions) in the non-aqueous solvent and supplies the non-aqueous solvent to the use point. The non-aqueous solvent to be purified is not particularly limited, and examples thereof include various organic solvents such as alcohol-based (isopropyl alcohol, methanol, ethanol, etc.), ether-based (propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), etc.), ketone-based (cyclohexanone, methyl isobutyl ketone, acetone, methyl ethyl ketone, etc.), alkene-based (2,4-diphenyl-4-methyl-1-pentene, 2-phenyl-1-propene, etc.), ester-based (propylene glycol monomethyl ether acetate, isopropyl acetate, etc.), aromatic-based, amine-based (N-methylpyrrolidone, etc.), and mixtures thereof.

[0014] The liquid purification device 10 has a purification means 11 including a monolithic organic porous ion exchanger. The inlet and outlet of the purification means 11 are respectively connected to a supply line L1 for flowing the non-aqueous solvent to be purified (the liquid to be purified) and a liquid delivery line L2 for flowing the purified non-aqueous solvent (the purified liquid). A sampling line L11 is connected to the supply line L1 via an on-off valve V1, and a sampling line L12 is also connected to the liquid delivery line L2 via an on-off valve V2. The sampling lines L11 and L12 are used to take out the liquid to be purified and the purified liquid, respectively, for analyzing the moisture content in the liquid to be purified and the purified liquid.

[0015] The monolithic organic porous ion exchanger as the purification means 11 is obtained by introducing an ion exchange group into the skeleton of a monolithic organic porous body, that is, a porous body having a large number of continuous pores serving as flow paths for the reaction solution between skeletons formed by an organic polymer. The monolithic organic porous ion exchanger has sufficient ion removal performance even when the treatment flow rate is increased compared with a general granular ion exchange resin, and thus is advantageous in that the apparatus can be miniaturized. As such a monolithic organic porous ion exchanger, at least one of a monolithic organic porous cation exchanger having a cation exchange group introduced as an ion exchange group and a monolithic organic porous anion exchanger having an anion exchange group introduced as an ion exchange group can be used according to the type of ion component to be removed.

[0016] Examples of the structure of the monolithic organic porous ion exchanger (hereinafter also referred to as "monolithic ion exchanger") used here include the open-cell structure disclosed in JP-A-2002-306976 and JP-A-2009-62512, the co-continuous structure disclosed in JP-A-2009-67982, the particle-aggregation type structure disclosed in JP-A-2009-7550, the particle-composite type structure disclosed in JP-A-2009-108294, and the like. Examples of the form of the monolithic ion exchanger and its production method include those disclosed in Patent Document 2. Examples of the ion exchange group introduced into the monolithic ion exchanger, that is, the cation exchange group introduced into the monolithic organic porous cation exchanger (hereinafter also referred to as "monolithic cation exchanger") and the anion exchange group introduced into the monolithic organic porous anion exchanger (hereinafter also referred to as "monolithic anion exchanger") include those disclosed in Patent Document 2.

[0017] During normal operation of the liquid purification apparatus 10, a purification process is performed in which the liquid to be purified is passed through the purification means 11 via the supply line L1. In this purification process, ionic components contained in the liquid to be purified are removed by the monolithic ion exchanger of the purification means 11, and the purified liquid thus obtained is sent to the point of use via the liquid delivery line L2. Here, the flow rate when the liquid to be purified is passed through the purification means 11 is not particularly limited, but is 500 to 5000 h in space velocity. -1 It is preferable that it be within the range of [specify range].

[0018] Furthermore, unused or regenerated monolithic ion exchangers may contain water, and in the purification process, such water may dissolve into the solution to be purified, potentially preventing the acquisition of a highly pure purified solution. Therefore, it is preferable to perform a pretreatment step to remove the water contained in the monolithic ion exchanger before the purification process. In the pretreatment step, a non-aqueous solvent for dehydration (dehydration solution) is passed through the purification means 11 via the supply line L1 to dehydrate the monolithic ion exchanger, and the water contained in the monolithic ion exchanger is dissolved into the dehydration solution and removed. The dehydration solution, which has thus absorbed water, is discharged to the outside through a drainage line (not shown) via the liquid supply line L2.

[0019] While a different type of non-aqueous solvent may be used as the dehydrating solution in the pretreatment step, in that case, it is necessary to pass the solution to be purified through the purification means 11 before the purification step to replace the dehydrating solution in the monolithic ion exchanger with the solution to be purified. Therefore, it is preferable to use the same type of non-aqueous solvent as the solution to be purified as the dehydrating solution. That is, for example, when purifying isopropyl alcohol (IPA) as the solution to be purified, it is preferable to use IPA as the dehydrating solution.

[0020] Furthermore, the non-aqueous solvent used as the dehydration solution is preferably of the highest possible purity. That is, the water concentration in the dehydration solution is preferably as low as possible, for example, preferably equal to or lower than the water concentration required for the purification solution. This reduces the amount of dehydration solution required for the dehydration of the monolithic ion exchanger. The concentrations of each ion in the dehydration solution are also preferably as low as possible, for example, preferably equal to or lower than the concentrations of each ion required for the purification solution. This prevents the ion exchange capacity of the monolithic ion exchanger from being consumed unnecessarily in the pretreatment step, thereby suppressing a shortened lifespan of the monolithic ion exchanger.

[0021] The pretreatment step is carried out until the water content of the monolithic ion exchanger in the purification means 11 is sufficiently reduced, and it is confirmed that almost no water is leaching out from the monolithic ion exchanger into the dehydration solution. Whether or not water is leaching out from the monolithic ion exchanger can be confirmed, for example, by comparing the water concentration in the dehydration solution before and after passing it through the purification means 11. That is, the dehydration solution is collected as a sample solution from sampling lines L11 and L12, respectively, and the water concentration in the collected sample solutions is measured. Then, it can be confirmed whether or not the leaching of water from the monolithic ion exchanger has almost stopped by whether or not the two values ​​match within a predetermined error range. Alternatively, it can be confirmed that the leaching of water from the monolithic ion exchanger has almost stopped when the water concentration in the dehydration solution after passing it through the purification means 11 (i.e., the water concentration in the sample water collected from sampling line L12) has sufficiently decreased and reached a steady state. Whether or not the moisture concentration has reached a steady state can be determined, for example, by comparing two time-series data points of moisture concentration and determining whether they match within a predetermined error range. As a method for measuring the moisture concentration in the dewatered liquid, it is preferable to use the Karl Fischer (KF) method, which is highly reliable and allows for accurate quantitative analysis of moisture.

[0022] In this embodiment, a monolithic ion exchanger is used as the purification means 11, and as described above, it is possible to pass the liquid at a higher space velocity. For this reason, in order to reduce the amount of dehydration solution required in the pretreatment step, it is considered preferable to dissolve the water contained in the monolithic ion exchanger into the dehydration solution in a short time at a relatively large flow rate, similar to that used in the purification step. However, in practice, our verification has shown that by passing the dehydration solution through the purification means 11 at a flow rate lower than that of the liquid to be purified in the purification step, the dehydration treatment of the monolithic ion exchanger can be completed with a smaller amount of dehydration solution. The experimental results that led to this finding will be described below.

[0023] The inventors passed a non-aqueous solvent as a dehydration solution through an unused monolithic ion exchanger and measured the change in water concentration in the dehydration solution over time. Specifically, IPA or a PGME / PGMEA mixed solution (PGME:PGMEA=7:3) was passed through a cylindrical container filled with a monolithic ion exchanger as the dehydration solution, and the water concentration in the dehydration solution, which was collected over time from the outlet of the container, was measured using the KF method. When IPA was used as the dehydration solution, the measurements were performed under the following six conditions (conditions A1-A3, B1-B3), and when the PGME / PGMEA mixed solution was used, the measurements were performed under the following three conditions (conditions C1-C3). The amount of dehydration solution required to pass through the monolithic ion exchanger until the water concentration in the dehydration solution reached a steady state was compared until the dehydration treatment of the monolithic ion exchanger was completed.

[0024] (Condition A1) A monolithic cation exchanger was used as the monolithic ion exchanger. A cylindrical container with an inner diameter of 8 mm and a height of 15 mm was used, and the flow rate of IPA when passing the liquid through the container was set to 25 mL / min. Therefore, the space velocity of the dewatered liquid was 1990 h -1 That was the case.

[0025] (Condition A2) A monolithic cation exchanger was used as the monolithic ion exchanger. A cylindrical container with an inner diameter of 22 mm and a height of 40 mm was used, and the flow rate of IPA when passing the liquid through the container was set to 30 mL / min. Therefore, the space velocity of the dewatered liquid was 118 h -1 That was the case.

[0026] (Condition A3) A monolithic cation exchanger was used as the monolithic ion exchanger. A cylindrical container with an inner diameter of 33.7 mm and a height of 70 mm was used, and the flow rate of IPA when passing the liquid through the container was set to 20 mL / min. Therefore, the space velocity of the dewatered liquid was 19 h -1 That was the case.

[0027] (Condition B1) Monolithic cation exchangers and monolithic anion exchangers were used as monolithic ion exchangers. Two cylindrical containers with an inner diameter of 10 mm and a height of 10 mm were connected in series. The upstream container was filled with monolithic anion exchangers, and the downstream container was filled with monolithic organic porous cation exchangers. The flow rate of IPA when passing the liquid through the containers was set to 25 mL / min. Therefore, the space velocity of the dewatered liquid was 955 h -1 That was the case.

[0028] (Condition B2) Monolithic cation exchangers and monolithic anion exchangers were used as monolithic ion exchangers. Two cylindrical containers with an inner diameter of 22 mm and a height of 20 mm were connected in series. The upstream container was filled with monolithic anion exchangers, and the downstream container was filled with monolithic cation exchangers. The flow rate of IPA when passing the liquid through the containers was set to 30 mL / min. Therefore, the space velocity of the dewatered liquid was 118 h -1 That was the case.

[0029] (Condition B3) As the monolithic ion exchanger, a monolithic cation exchanger and a monolithic anion exchanger were used. As the cylindrical container, two containers with an inner diameter of 22 mm and a height of 20 mm connected in series were used. The upstream container was filled with the monolithic anion exchanger, and the downstream container was filled with the monolithic cation exchanger. The flow rate of IPA when passing the liquid through the container was set to 5 mL / min. Therefore, the space velocity of the dehydration treatment liquid was 20 h -1 It was.

[0030] (Condition C1) As the monolithic ion exchanger, a monolithic cation exchanger was used. As the cylindrical container, a container with an inner diameter of 10 mm and a height of 10 mm was used, and the flow rate of the PGME / PGMEA mixed solution when passing the liquid through the container was set to 33.3 mL / min. Therefore, the space velocity of the dehydration treatment liquid was 2545 h -1 It was.

[0031] (Condition C2) As the monolithic ion exchanger, a monolithic cation exchanger was used. As the cylindrical container, a container with an inner diameter of 22 mm and a height of 20 mm was used, and the flow rate of the PGME / PGMEA mixed solution when passing the liquid through the container was set to 15 mL / min. Therefore, the space velocity of the dehydration treatment liquid was 118 h -1 It was.

[0032] (Condition C3) As the monolithic ion exchanger, a monolithic cation exchanger was used. As the cylindrical container, a container with an inner diameter of 22 mm and a height of 20 mm was used, and the flow rate of the PGME / PGMEA mixed solution when passing the liquid through the container was set to 2.5 mL / min. Therefore, the space velocity of the dehydration treatment liquid was 20 h -1 It was.

[0033] Figures 2(a) to 2(c) are graphs showing the measurement results under conditions A1 to A3, Figures 3(a) to 3(c) are graphs showing the measurement results under conditions B1 to B3, and Figures 4(a) to 4(c) are graphs showing the measurement results under conditions C1 to C3. The horizontal axis of the graphs represents the volume ratio (volume ratio of total volume flowing through to the amount packed in the monolithic ion exchanger), and the vertical axis represents the water concentration in the dewatered liquid on a logarithmic scale. The dashed lines in the graphs are auxiliary lines to make it easier to understand that the water concentration in the dewatered liquid has reached a steady state.

[0034] Comparing conditions A1 to A3 where monolithic cation exchangers were used individually, the volume of fluid passed through until dehydration was completed was approximately 4000 BV under condition A1, approximately 40 BV under condition A2, and approximately 100 BV under condition A3. Similarly, comparing conditions C1 to C3 where monolithic cation exchangers were used individually, the volume of fluid passed through until dehydration was completed was approximately 350 BV under condition C1, approximately 70 BV under condition C2, and approximately 80 BV under condition C3. Furthermore, comparing conditions B1 to B3 where monolithic cation exchangers and monolithic anion exchangers were used in combination, the volume of fluid passed through until dehydration was completed was approximately 3000 BV under condition B1, approximately 150 BV under condition B2, and approximately 100 BV under condition B3. Therefore, these results confirm that when the dehydration solution was passed through at a lower flow rate than during the purification process (conditions A2-A2, B2-B3, C2-C3), the total volume of solution passed through until the dehydration process was completed was smaller compared to when the dehydration solution was passed through at a flow rate similar to that during the purification process (conditions A1, B1, C1). This is thought to be because passing the dehydration solution through at a relatively low flow rate ensured sufficient and reliable contact between the monolithic ion exchanger, which has a large specific surface area, and the dehydration solution.

[0035] Thus, according to this embodiment, the flow rate of the liquid to be purified during the purification process (for example, 500 to 5000 h in space velocity) -1 A flow rate less than (for example, 10-500 h⁻¹ in space velocity) -1It is preferable to pass the dehydration solution through the pretreatment process. This makes it easier to remove water contained in the monolithic ion exchanger of the purification means 11, and reduces the amount of dehydration solution required to complete the dehydration process. [Explanation of Symbols]

[0036] 10 Liquid purification equipment 11 Purification means L1 supply line L2 liquid delivery line L11, L12 sampling lines V1, V2 Shut-off valves

Claims

1. A method for operating a liquid purification apparatus having a monolithic organic porous ion exchanger as a purification means for purifying a non-aqueous solvent, A step of passing the non-aqueous solvent to be purified or a non-aqueous solvent other than the non-aqueous solvent to be purified as a dehydration solution through the purification means, and dissolving and removing the water contained in the purification means into the dehydration solution, The process includes removing water contained in the purification means, passing the non-aqueous solvent to be purified through the purification means, and removing ionic components contained in the non-aqueous solvent by the purification means, A method for operating a liquid purification apparatus, wherein the flow rate at which the dewatered liquid is passed through the purification means is less than the flow rate at which the non-aqueous solvent to be purified after the water contained in the purification means is passed through the purification means.

2. The flow rate of the dehydration treatment liquid is 10 to 500 hours. －１ A method for operating the liquid purification apparatus according to claim 1, performed at a spatial velocity of [value].

3. The non-aqueous solvent to be purified is passed through for 500 to 5000 hours. －１ A method for operating the liquid purification apparatus according to claim 2, performed at a spatial velocity of [value].

4. A method for operating a liquid purification apparatus according to any one of claims 1 to 3, wherein the purification means is at least one of a monolithic organic porous cation exchanger and a monolithic organic porous anion exchanger.

5. A method for operating a liquid purification apparatus according to any one of claims 1 to 3, wherein the non-aqueous solvent is an alcohol or an ether.

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