JP5762863B2 - Method and apparatus for purifying alcohol - Google Patents

Description

  The present invention relates to a method and apparatus for purifying alcohol, and more particularly, to a method and apparatus suitable for purifying and recycling recovered alcohol.

  Alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol (IPA) are used in large quantities as cleaning agents, solvents, and synthetic raw materials for the chemical industry. In particular, in the semiconductor device manufacturing process, a large amount of IPA is used for applications such as cleaning and drying. For example, an IPA evaporative drying method for removing moisture after performing pure water cleaning on a semiconductor device is effective as a step of removing moisture, but on the other hand, it has high volatility and high purity IPA. As a result, there is a problem that the manufacturing cost of the semiconductor device becomes high. Therefore, it is desired to recover and reuse the waste IPA used in the semiconductor device manufacturing process in terms of cost reduction and improvement of environmental load. The IPA discharged in the semiconductor device manufacturing process contains impurities derived from the manufacturing process, materials, and equipment. In order to recover and reuse the IPA, these impurities are highly removed. It is necessary to purify the IPA to the same extent as when purchased for the semiconductor device manufacturing process. Main components of impurities include moisture, ionic impurities, metals, and fine particles. In commercially available IPA, grades are set according to the use (for example, for semiconductor device manufacturing process) and the like, and a standard value for each impurity is determined for each grade.

  When IPA is used in, for example, cleaning and drying steps in semiconductor device manufacturing, the moisture concentration in the IPA is 0.1% or less, and the concentration of the metal component is 0.1 ppb or less, preferably 0.01 ppb or less. Is done.

  A distillation method is known as a method for purifying contaminated alcohol containing impurities. However, using only the distillation method to purify alcohol to a desired purity requires a large-scale distillation facility, which increases the equipment cost and installation area, necessitates a large amount of energy, and increases the energy cost. It is not preferable in terms of the aspect.

  For each impurity that may be contained in the alcohol, a method for removing those impurities from the alcohol has been proposed as shown below.

  For example, as a method for efficiently removing moisture in alcohol, Patent Document 1 discloses that an osmotic vaporization method is used to reduce the moisture concentration in alcohol to a certain level or less, and an adsorbent such as zeolite is used. A method for adsorbing and removing moisture is shown. Patent Document 2 discloses that an anion exchange membrane is used as a separation membrane in a vapor permeation (VP) method to separate water from alcohol and further purify the alcohol by distillation.

  The pervaporation (PV) method uses a separation membrane that has an affinity for a component to be separated (for example, moisture), and separates the mixed solution (for example, alcohol containing moisture as an impurity) into the separation membrane. In this case, separation is performed by the difference in permeation speed of each component in the separation membrane by reducing the pressure on the permeation side of the separation membrane or flowing an inert gas. In the pervaporation method, a method in which the permeation side of the separation membrane is under reduced pressure is called a vapor permeation method. In Patent Document 1, a polyimide separation membrane or a cellulose separation membrane is used as a separation membrane, but a zeolite membrane is also widely used as a separation membrane for dehydration from alcohol. Zeolite membranes have extremely strong hygroscopicity, and with regard to adsorption of polar molecules such as water molecules, separation performance is high even when the partial pressure of the molecular species is extremely low, and loss of the target alcohol is small. , Has the characteristics.

  As a method for removing ionic impurities, as shown in Patent Document 3 and Non-Patent Document 1, a method using an ion exchange resin is known. The treatment with an ion exchange resin is simpler with less energy and equipment costs than using a distillation apparatus, and can provide a highly pure alcohol. In the method using an ion exchange resin, an alcohol-containing liquid is passed through the ion exchange resin layer. However, in Patent Document 4, an ion exchange membrane is used instead of an ion exchange resin, and a filter and an ion exchange membrane are combined. A method for removing cationic impurities such as metal ions and fine particles has been proposed.

  Patent Document 5 discloses that an alcohol from which moisture has been removed by pervaporation is further distilled to remove metal and pass through a microfiltration membrane to remove insoluble fine particles.

  Patent Document 6 discloses a reproduction system in which various methods as described above are combined, the IPA recovered from the semiconductor device manufacturing process is purified and supplied again to the semiconductor device manufacturing process, and such a reproduction system. A purification method is disclosed.

Japanese Patent Laid-Open No. 11-276801 JP-A-6-69175 JP 2009-57286 A JP 2005-263729 A JP-A-9-57069 JP-A-11-57304

Partha V. Buragohain, William N. Gill, and Steven M. Cramer; "Novel Resin-Based Ultrapurification System for Reprocessing IPA in the Semiconductor Industry," Ind. Eng. Chem. Res., 1996, 35 (9), pp. 3149-3154

  As described above, various methods are known as a method for purifying alcohol such as IPA. Among these, the method combining the pervaporation membrane and the adsorbent as shown in Patent Document 1 can reduce the moisture in the alcohol, but the energy consumption related to the regeneration of the adsorbent becomes very large, and the cost is low. This may lead to an increase in the amount, and the elution from the adsorbent may cause a load on the subsequent distillation apparatus. In the method combining vapor permeation and distillation using an anion exchange membrane as shown in Patent Document 2, the separation factor of water with respect to IPA is about 160, which is compared with the separation factor of about 1000 when a zeolite membrane is used. Therefore, the device scale becomes large. Moreover, when performing distillation, there exists a possibility that the particle (for example, metal microparticles) originating in the member which comprises a distillation apparatus may mix in refined alcohol.

  Alcohol purification methods using ion exchange resins have been proposed as typified by Patent Document 3, but alcohol has a lower diffusion rate in the ion exchange resin than water, and the ion exchange reaction in the ion exchange resin is less likely to occur. Since the reaction rate is also low, when removing ionic impurities in the alcohol, it is necessary to set the liquid passing rate through the ion exchange resin to be smaller than when removing ionic impurities in the aqueous solution. Furthermore, a general ion exchange resin holds about 40 to 60% of moisture inside the ion exchange resin itself. When an ion exchange resin is used for the purification of alcohol, the water already held by the ion exchange resin may be eluted into the alcohol. Before using for purification of alcohol, it is possible to pass alcohol through the ion exchange resin in advance and replace the water in the ion exchange resin with alcohol. There is a problem that it takes time.

  Furthermore, in a method combining a filter and an ion exchange membrane as shown in Patent Document 4, moisture and anionic impurities cannot be removed by this method alone.

  Furthermore, the present inventors have confirmed through experiments that the metal concentration of the liquid after passing through the dehydration membrane has increased and that these metals cannot be reduced to a very small amount (less than 0.01 ppb) by distillation operation. That is, the IPA regeneration system and purification method disclosed in Patent Document 6 have a problem that the metal concentration in the alcohol purification solution cannot be less than 0.01 ppb.

  An object of the present invention is to provide a method and apparatus suitable for recovering and purifying alcohol typified by IPA, which can reduce the amount of metal contained in the purified alcohol to a very small amount. There is.

  As a result of repeated studies to solve the above problems, the present inventors conducted ion exchange on an alcohol-containing liquid such as recovered alcohol to remove ionic components, and then passed through the dehydration membrane. It was discovered that by performing ion exchange again in the latter stage, it is possible to obtain an alcohol in which the contained metal is reduced to a very small amount, and the present invention has been completed.

  That is, the method for purifying alcohol according to the present invention includes a first ion exchange step for performing an ion exchange treatment on an alcohol-containing liquid, and a dehydration treatment for the liquid treated in the first ion exchange step using a dehydration membrane. And a second ion exchange step of further performing ion exchange treatment on the dehydrated liquid to obtain purified alcohol.

  The alcohol purification apparatus of the present invention includes a first ion exchange means for performing an ion exchange treatment on an alcohol-containing liquid, and a dehydration membrane for dehydrating the liquid treated by the first ion exchange means by pervaporation or vapor permeation. And a second ion exchange means for obtaining purified alcohol by further subjecting the liquid dehydrated by the dehydration membrane to ion exchange treatment.

  According to the present invention, by combining the dehydration treatment with the dehydration membrane, the first ion exchange step before the dehydration treatment, and the second ion exchange treatment after the dehydration treatment, impurities such as metal components contained in the alcohol The amount can be reduced to a very small amount, and the alcohol can be purified with high efficiency.

It is a figure which shows the structure of the alcohol refiner | purifier of the 1st Embodiment of this invention. It is a figure which shows the structure of an alcohol refinement | purification apparatus provided with a microfiltration membrane. It is a graph which shows the time change of the moisture concentration in an ion exchange resin exit and an ion adsorption membrane exit.

  The alcohol purification apparatus 20 according to the first embodiment of the present invention shown in FIG. 1 is preferably used for recovering and purifying alcohol containing impurities discharged from various processes such as a semiconductor device manufacturing process. Is. In the example shown in FIG. 1, the alcohol to be purified is IPA (isopropyl alcohol), and the IPA used in the semiconductor device manufacturing apparatus 12 and containing impurities is recovered. The recovered IPA is purified, and the purified IPA is supplied again to the semiconductor device manufacturing apparatus 12 via the supply tank 11. The supply tank 11 is supplied with supplemental alcohol in order to make up for the shortage required at the start of operation or during operation.

  In the alcohol refining apparatus 20, there are a recovery tank 21 that temporarily holds IPA recovered from the semiconductor device manufacturing apparatus 12 as an alcohol-containing liquid, and a pump 22 that is provided at the outlet of the recovery tank 21 and feeds the alcohol-containing liquid. The first ion exchange means 23, the dehydration membrane 24, and the second ion exchange means 25 are connected in series in this order to the outlet of the pump 22, and the purified alcohol is supplied to the second ion exchange. Obtained from means 25. The purified alcohol from the second ion exchange means 25 is returned to the supply tank 11 via a pipe for reuse in the semiconductor device manufacturing apparatus 12.

  The 1st ion exchange means 23 performs an ion exchange process with respect to the alcohol containing liquid which flows in from the pump 22, and removes the ion component in alcohol containing liquid using an ion exchange resin. The first ion exchange means 23 can be used without particular limitation as long as it has an ion exchange action, but considering that it is a part of the first stage in the purification process of the recovered alcohol. It is preferable to use an ion exchange resin having a large exchange capacity. The ion exchange resin is, for example, a fine particle and is filled in, for example, a tower-like container. When performing the ion exchange treatment, the alcohol-containing liquid is allowed to flow into the container so that the alcohol-containing liquid passes through the ion-exchange resin layer. By performing the ion exchange treatment by the first ion exchange means 23, it is possible to reduce the ion load such as acid or ionic metal that causes deterioration of the dehydration film 24 in the subsequent stage and to extend the life of the dehydration film 24. it can. The first ion exchange means 23 is configured, for example, such that a tower-like container is filled with an ion exchange resin, and the liquid passes through the ion exchange resin layer. Among the ion exchange resins, the cation exchange resin adsorbs and removes cations such as Na ions and Ca ions, and the anion exchange resin adsorbs and removes anions such as Cl ions. The specifications and apparatus configuration of the cation exchange resin and the anion exchange resin filled in the first ion exchange means 23 are the properties of IPA supplied to the first ion exchange means 23 as an alcohol-containing liquid, and this alcohol purification apparatus. Although it is determined according to the required quality in the purified alcohol delivered from No. 20, from the viewpoint of adsorption performance and low elution, H (hydrogen ion) type strongly acidic cation exchange resin (SACER), OH (hydroxide ion) It is desirable to use a form of strongly basic anion exchange resin (SBAER).

  As the ion exchange resin, a cation exchange resin or anion exchange resin provided in a single bed, a cation exchange resin and an anion exchange resin provided in multiple beds, or a mixed bed of a cation exchange resin and an anion exchange resin. However, in order to reduce the load of ions such as acids and ionic metals that cause deterioration of the dehydration film 24 in the subsequent stage, a mixed bed is preferable. When it is required to reduce the water concentration in the final purified alcohol or when it is desired to reduce water elution from the ion exchange resin immediately after the ion exchange resin is replaced, the ion exchange resin does not contain water. It is preferable to use a dry resin.

  In the alcohol purification method according to the present invention, the liquid flowing out from the first ion exchange means 23 is dehydrated to remove moisture. As a method for removing moisture, it is preferable to perform membrane dehydration by pervaporation (PV) or vapor permeation (VP). Therefore, in the alcohol purifying apparatus shown in FIG. 1, the dehydration membrane 24 is used to perform membrane dehydration by pervaporation (PV) or vapor permeation (VP) on the liquid treated by the first ion exchange means 23. Concentrate alcohol. The dehydration membrane 24 is configured as, for example, a water permeable membrane module, and a membrane made of a polymer material such as polyimide, cellulose, or polyvinyl alcohol, or an inorganic material such as zeolite is used as the membrane. Can do. In addition, it is preferable that the water concentration in the alcohol is 0.1% or less at the outlet of the dehydration film 24.

  The second ion exchange means 25 provided at the subsequent stage of the dehydration membrane 24 can reduce and remove ions eluted from members such as the dehydration membrane and piping. By reducing / removing ionic impurities in the second ion exchange means 25, higher purity alcohol can be obtained. In the system described in Patent Document 6, metal ions are removed by distillation after removing ionic impurities, and then water is removed by a dehydration film. The present inventors have found that the metal concentration of the liquid after passing through the dehydration membrane is increased, and that these metals cannot be reduced to a very small amount (less than 0.01 ppb) by distillation operation. Therefore, in the alcohol purification method of the present invention, the metal is removed by ion exchange (second ion exchange means) after passing through the first ion exchange means and removing moisture with the dehydration membrane.

  As the second ion exchange means 25 for reducing the metal to a very small amount, an ion exchange resin or an ion adsorption membrane can be used, but as a high purity alcohol purification which is the final object of the present invention, It is preferable to use an ion adsorption film. The inventors of the present invention can rapidly replace the moisture and alcohol possessed by the ion-adsorbing membrane in the matrix with respect to the ion-exchange resin up to the target water concentration, and also have an ion exchange reaction rate. I found it excellent. Therefore, by adopting an ion adsorption membrane as the second ion exchange means, not only the metal is removed to a very small amount, but also the water concentration in the alcohol is not increased, so that higher purity alcohol can be purified. . The ion adsorption membrane has a porous membrane material and has an ion exchange function. Such an ion-adsorbing membrane is not particularly limited as long as it has a pore size of 100 μm or less and has an ion exchange function, and there are no particular restrictions on the material or model thereof. A material having a functional group having ion exchange ability introduced on the surface of the membrane material can be used. Examples of the shape of the membrane material include a pleat type, a flat membrane type, a hollow fiber type, and a porous body as described in JP-A No. 2003-112060. As the ion exchange group introduced into the membrane material, it is possible to use either a cation exchange group, a chelate exchange group, an anion exchange group, or a combination of at least two of these depending on the components to be eluted. it can.

  In the example shown in FIG. 1, the liquid flowing out from the second ion exchange means 25 circulates in the supply tank 11 as purified alcohol, but a filter for removing particulates is provided at the subsequent stage of the second ion exchange means 25. The liquid that has passed through the filter may be circulated to the supply tank 11 as purified alcohol. In order to obtain a necessary permeation flow rate, it is preferable to use a microfiltration membrane as a filter. FIG. 2 shows the alcohol purification apparatus 20 shown in FIG. 1, in which a microfiltration membrane 26 is provided at the subsequent stage of the second ion exchange means 25, and the liquid passed through the microfiltration membrane 26 is circulated to the supply tank 11 as purified alcohol. The structure which was made to do is shown.

  Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the following examples.

[Example 1]
In the configuration shown in FIG. 1, the part of the alcohol purifier 20 was assembled. As the first ion exchange means 23, a gel-type ion exchange resin (mixed bed ion exchange resin of strongly acidic cation exchange resin and strongly basic anion exchange resin) ESG-2 manufactured by Organo Corporation is used. It was. As the dehydration membrane 24, a membrane made of A-type zeolite was used, and dehydration treatment was performed by a vapor permeation method. As the second ion exchange means 25, an ion adsorption membrane module manufactured by Asahi Kasei Corporation was used.

  An alcohol-containing liquid having a water concentration of 5% in IPA is supplied to the recovery tank 21, and the first ion exchange means 23, the dehydration membrane 24, and the second ions are set by the pump 22 at a flow rate of 2 kg / hour. The alcohol-containing liquid is passed in the order of the exchange means 25, and each of the recovery tank 21, the first ion exchange means (ion exchange resin) 23, the dehydration membrane 24, and the second ion exchange means (ion adsorption membrane) 25 is used. The water concentration and metal concentration at the outlet were measured. A Karl Fischer moisture concentration meter (manufactured by Hiranuma Sangyo Co., Ltd.) was used to measure the moisture concentration, and an ICP-MS (inductively coupled plasma mass spectrometer) was used to measure the metal concentration. The metal concentration measurement targets were sodium (Na), aluminum (Al), iron (Fe), calcium (Ca), chromium (Cr) and nickel (Ni) ions. The lower limit of analysis for each metal ion in the metal concentration measurement was 0.01 ppb. The results of moisture concentration measurement are shown in Table 1, and the results of metal concentration measurement are shown in Table 2.

  As shown in Table 1, the water concentration in the liquid was stable after the dehydration film 24 and was 0.1% or less. As shown in Table 2, regarding the metal concentration, it was observed that the metal concentration significantly decreased by passing through the first ion exchange means 23 made of ion exchange resin, but at the outlet of the dehydration membrane 24. The concentration of some metals increased due to elution of metals considered to be derived from components. However, it has been confirmed that at the outlet of the second ion exchange means 25 made of an ion-adsorbing film, the concentration of all metal components is removed to a level below the lower limit of analysis.

[Comparative Example 1]
In the alcohol refining apparatus of Example 1, an alcohol refining apparatus provided with a distillation apparatus instead of the second ion exchange means 25 composed of an ion adsorption membrane is assembled, and the alcohol-containing liquid is passed and recovered in the same manner as in Example 1. The water concentration and metal concentration at the outlet of each of the tank 21, the first ion exchange means (ion exchange resin) 23, the dehydration membrane 24 and the distillation apparatus were measured. The results for water concentration are shown in Table 3, and the results for metal concentration are shown in Table 4.

  Regarding the water concentration, the water concentration in the liquid was stable after the dehydration film 24 and was 0.1% or less. However, regarding the metal concentration, the metal concentration increased by passing through the dehydration film 24 was measured in the distillation apparatus. It could not be reduced sufficiently, and for some elements, the metal ion concentration could not be reduced below 0.01 ppb.

[Example 2]
The ease of alcohol substitution was examined for ion exchange resins and ion adsorption membranes. An ion adsorption membrane module (produced by Asahi Kasei Co., Ltd.) washed with ultrapure water and a column filled with an ion exchange resin (produced by Organo Corp.) washed with ultrapure water were prepared. The liquid concentration at each outlet was measured using a Karl Fischer water concentration meter (manufactured by Hiranuma Sangyo Co., Ltd.) until the water content was reduced to a predetermined water concentration (0.1%) or less. FIG. 3 shows the relationship between the liquid passing time and the amount of water at that time. As shown in FIG. 3, in the ion adsorption membrane, the water concentration at the outlet became 0.1% or less within 20 minutes from the start of liquid flow. On the other hand, with the ion exchange resin, the moisture concentration at the outlet was 0.1% or more even after 1 hour or more had elapsed from the start of liquid passage. From this result, it can be seen that the moisture content of the ion adsorption membrane can be replaced with alcohol more rapidly than the ion exchange resin. Therefore, it is understood that it is preferable to use an ion adsorption membrane rather than an ion exchange resin as the second ion exchange means 25 provided in the subsequent stage of the dehydration membrane 24.

DESCRIPTION OF SYMBOLS 11 Supply tank 12 Semiconductor device manufacturing apparatus 20 Alcohol refiner 21 Recovery tank 22 Pump 23 1st ion exchange means 24 Dehydration membrane 25 2nd ion exchange means 26 Microfiltration membrane

Claims (10)

A first ion exchange step for performing an ion exchange treatment on the alcohol-containing liquid;
Dehydrating the liquid processed in the first ion exchange step;
A second ion exchange step of further performing an ion exchange treatment on the dehydrated liquid to obtain purified alcohol;
A method for purifying an alcohol having   The method for purifying alcohol according to claim 1, wherein the second ion exchange step is a step of passing through an ion adsorption membrane.   The method for purifying alcohol according to claim 1 or 2, wherein the first ion exchange step is a step of passing through an ion exchange resin.   The method of purifying alcohol according to claim 3, wherein the ion exchange resin is an ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed.   The method for purifying alcohol according to any one of claims 1 to 4, wherein the alcohol-containing liquid is a liquid containing isopropyl alcohol, and purifies isopropyl alcohol. First ion exchange means for performing ion exchange treatment on the alcohol-containing liquid;
A dehydration membrane for dehydrating the liquid treated by the first ion exchange means by pervaporation or vapor permeation;
A second ion exchange means for obtaining purified alcohol by further performing ion exchange treatment on the liquid dehydrated by the dehydration membrane;
An alcohol refining apparatus.   The alcohol purification apparatus according to claim 6, wherein the second ion exchange means comprises an ion adsorption membrane.   The alcohol purification apparatus according to claim 6 or 7, wherein the first ion exchange means is made of an ion exchange resin.   The alcohol purification apparatus according to claim 8, wherein the ion exchange resin is an ion exchange resin in which a cation exchange resin and an anion exchange resin are mixed.   The alcohol-purifying apparatus according to any one of claims 6 to 9, wherein the alcohol-containing liquid is a liquid containing isopropyl alcohol and purifies isopropyl alcohol.

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