Organic solvent and purification method thereof

Abstract

The present invention relates to an organic solvent and a method for purifying the same, the method for purifying the organic solvent comprising the steps of: (a) supplying the organic solvent to a distillation column to perform distillation; and (b) a step for discharging a portion of the organic solvent containing impurities through a side discharge flow connected to the lower end of the distillation column, in which the discharge in the step (b) is discharged at a flow rate of 0.5-10% of the input flow rate of the organic solvent supplied to the distillation column in the step (a).

Description

Technical Field

[0001] The present invention relates to an organic solvent and a method for purifying the same. Background Art

[0002] Organic solvents used as process liquids for various purposes such as cleaning liquids in semiconductor processes are managed at high purity by controlling the total amount of impurities. Increased content of the above impurities may lead to substrate contamination, poor process, wafer defects, etc. Specifically, if the above impurities are contained in the organic solvent, errors will occur when forming the pattern, or the adhesion of the evaporated film will be hindered. In addition, during the thermal process, the remaining organic pollutants may also react with the silicon substrate to form compounds such as silicon carbide. As a result, the electrical properties of the semiconductor circuit may be damaged, ultimately affecting the performance stability and overall productivity of the device containing the semiconductor circuit.

[0003] In addition, according to the management conditions of the above-mentioned organic solvents, the removed organic impurities can also be regenerated, one of which is acetone. The generation of acetone will reduce the purity of the refined solvent and reduce the cleaning power, which in turn leads to a decrease in the process yield, and thus cannot play a satisfactory solvent function in the semiconductor process.

[0004] Korean Patent Publication No. 10-2021-0070275 discloses a method for producing isopropyl alcohol by directly hydrating water in propylene, the method comprising: a distillation step of distilling crude isopropyl alcohol; and a filtering step of filtering the isopropyl alcohol obtained by the distillation step using a filter having an ion exchanger.

[0005] However, the prior art may have the problem that even after purification, organic impurities such as acetone and / or metal impurities may remain and cannot be fully removed. In addition, the impurities may be regenerated during the storage of the purified organic solvent.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Korean Patent Publication No. 10-2021-0070275 Summary of the invention

[0009] Issues to be solved

[0010] In order to solve the above-mentioned problems, an object of the present invention is to provide a method for purifying an organic solvent, wherein a step is provided in which impurities having a relatively high boiling point are continuously discharged at a constant flow rate together with a part of the organic solvent through a side discharge stream connected to the lower end of a distillation tower, thereby effectively removing organic impurities such as n-propyl alcohol and / or metal impurities to obtain an organic solvent with high purity.

[0011] Another object of the present invention is to control the storage temperature of the purified organic solvent to suppress the regeneration of organic impurities such as acetone even during long-term storage.

[0012] Another object of the present invention is to provide a high-purity organic solvent obtained by continuously discharging impurities having a relatively high boiling point at a constant flow rate through a side discharge flow.

[0013] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and a person skilled in the art should be able to clearly understand other problems not mentioned through the following description.

[0014] Solution to the problem

[0015] The present invention relates to a method for purifying an organic solvent, characterized in that it comprises: (a) supplying an organic solvent to a distillation tower to perform distillation; and (b) discharging a portion of the organic solvent containing impurities through a side discharge stream connected to a lower end of the distillation tower, wherein the discharge in the step (b) is performed at a flow rate of 0.5 to 10% of the input flow rate of the organic solvent supplied to the distillation tower in the step (a).

[0016] In the present invention, the organic solvent may be an alcohol-based organic solvent.

[0017] In the present invention, the organic solvent may be at least one selected from isopropyl alcohol, propanol, butanol and hexyl alcohol.

[0018] In the present invention, the impurities may have a boiling point higher than or equal to that of the organic solvent.

[0019] In the present invention, the impurities may include one or more selected from n-propanol, 2-pentanone, 4-methyl-2-pentanone, 2-butanol, isopropyl acetate, nonanaldehyde, decanaldehyde, t-amyl alcohol, diacetone alcohol and metal impurities.

[0020] In the present invention, the discharge in step (b) may be carried out at a flow rate of 1.0 to 10% of the input flow rate of the organic solvent supplied to the distillation tower in step (a).

[0021] In the present invention, the discharge in the step (b) can be carried out as a continuous process.

[0022] In the present invention, the content of one or more metals among iron (Fe), chromium (Cr), nickel (Ni) and copper (Cu) contained in the organic solvent can be reduced to 30% or less.

[0023] The present invention may further include a step of storing the purified organic solvent at a temperature lower than 35°C.

[0024] The present invention may further include a step of storing the purified organic solvent at a temperature of 30° C. or lower.

[0025] The present invention may further include one or more of the following steps: a step of removing water contained in the organic solvent before the above step (a); a step of re-vaporizing the liquefied impurities discharged from the lower end of the distillation tower after the above step (a) and before the above step (b); a step of liquefying the distilled organic solvent by a condenser after the above step (a); and a step of refluxing the organic solvent distilled in the distillation tower after the above step (a).

[0026] The present invention relates to an organic solvent, wherein the content of one or more of n-propyl alcohol, 2-pentanone, 4-methyl-2-pentanone, 2-butanol, isopropyl acetate, nonanaldehyde, decanaldehyde, t-amyl alcohol and diacetone alcohol is 2 ppm or less, and the content of one or more of iron (Fe), chromium (Cr), nickel (Ni) and copper (Cu) is 5 ppt or less, and the organic solvent comprises an organic solvent purified by the above-mentioned organic solvent purification method.

[0027] Effects of the Invention

[0028] According to the method for refining an organic solvent of the present invention, since the organic solvent containing impurities is continuously discharged at a flow rate of 0.5 to 10%, more preferably 1.0 to 10%, through the side discharge flow, the purity of the purified organic solvent can be further improved. Specifically, according to the present invention, organic impurities such as n-propyl alcohol and / or metal impurities contained in the organic solvent can be effectively controlled.

[0029] In addition, according to the method for purifying an organic solvent of the present invention, since the purified organic solvent is stored at a temperature lower than 35° C., preferably at a temperature lower than 30° C., regeneration of organic impurities such as acetone can be suppressed, thereby providing a purified organic solvent with reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process diagram showing a method for purifying an organic solvent according to one embodiment of the present invention.

[0031] Explanation of symbols

[0032] 100: Refining Tower

[0033] 110: Raw material tank

[0034] 111: Drying bed

[0035] 120: Distillation Tower

[0036] 121: Reboiler

[0037] 122: Reflux tank

[0038] 130: Side discharge flow

[0039] 140: Impurity discharge tank

[0040] 150: Product tank DETAILED DESCRIPTION

[0041] The present invention provides a method for purifying an organic solvent, characterized by comprising: (a) supplying an organic solvent to a distillation tower to perform distillation; and (b) discharging a portion of the organic solvent containing impurities through a side discharge stream connected to the lower end of the distillation tower, wherein the discharge in the step (b) is carried out at a flow rate of 0.5 to 10% of the input flow rate of the organic solvent supplied to the distillation tower in the step (a), thereby providing a purified organic solvent with high purity. In addition, the scope of the present invention includes an organic solvent purified by the above-mentioned method for purifying an organic solvent and a method for storing the organic solvent.

[0042] <Method for Purifying Organic Solvent>

[0043] The method for purifying an organic solvent of the present invention is characterized by comprising a step of continuously discharging a portion of the organic solvent containing impurities at a specific flow rate in the distillation step. Specifically, by discharging the raw material containing impurities accumulated at the bottom of the above-mentioned tower at a certain ratio, it is possible to prevent the concentration of the material that continues to reflux in the distillation tower and falls to the bottom of the distillation tower, thereby improving the purity of the finally purified organic solvent. In the present invention, the raw material may refer to the organic solvent before purification.

[0044] More specifically, the method for purifying an organic solvent of the present invention may include: (a) supplying an organic solvent to a distillation tower to perform distillation; and (b) discharging a portion of the organic solvent containing impurities through a side discharge stream connected to the lower end of the distillation tower, wherein the discharge in the step (b) may be performed at a flow rate of 0.5 to 10% of the input flow rate of the organic solvent supplied to the distillation tower in the step (a), thereby providing a purified organic solvent with high purity.

[0045] When the method for purifying an organic solvent of the present invention is used, organic impurities and / or metal impurities can be effectively reduced.

[0046] The organic solvents include, for example, methanol, ethanol, 1-propanol, isopropanol, n-propanol, 2-methyl-1-propanol, n-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, n-hexanol, cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 2,2-dimethyl-3-pentanol, 2,3-dimethyl-3-pentanol , 2,4-dimethyl-3-pentanol, 4,4-dimethyl-2-pentanol, 3-ethyl-3-heptanol, 1-heptanol, 2-heptanol, 3-heptanol, 2-methyl-2-hexanol, 2-methyl-3-hexanol, 5-methyl-1-hexanol, 5-methyl-2-hexanol, 2-ethyl-1-hexanol, methylcyclohexanol, trimethylcyclohexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol, 1-octanol, 2-octanol, 3-octanol, 2-propyl-1-pentanol, 2,6-dimethyl-4-heptanol, 2-nonanol, 3,7-dimethyl-3-octanol, ethylene glycol, propylene glycol, diethyl ether, dipropyl ether, diisopropyl ether, butyl methyl ether, butyl ethyl ether, butyl propyl ethyl ether, dibutyl ether, diisobutyl ether, tert-butyl methyl ether, tert-butyl ethyl ether, tert-butyl propyl ether, di-tert-butyl ether, diamyl ether, diisoamyl ether, cyclopentyl methyl ether, cyclohexyl methyl ether, bromomethyl methyl ether, α,α-dichloromethyl methyl ether, chloromethyl ethyl ether, 2-chloroethyl methyl ether, 2-bromoethyl methyl ether, 2,2-dichloroethyl methyl ether, 2-chloroethyl ethyl ether, 2-bromoethyl ethyl ether, (±)-1,2-dichloroethyl ethyl ether, 2,2,2-trifluoroethyl ether, ethyl vinyl ether, butyl vinyl ether, allyl ethyl ether, allyl propyl ether, allyl butyl ether, diallyl ether, 2-methoxypropylene, ethyl-1-propenyl ether, cis -1-bromo-2-ethoxyethylene, 2-chloroethyl vinyl ether, allyl-1,1,2,2-tetrafluoroethyl ether, octane, isooctane, nonane, decane, methylcyclohexane, decalin, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, sec-butylbenzene, methylisopropylbenzene, dipentene, methyl pyruvate, monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, methyl methoxypropionate, cyclopentanone, cyclohexanone, n-butyl acetate, γ-butyrolactone, diisoamyl ether, isoamyl acetate, chloroform, dichloromethane, 1,4-dioxane, hexanol, 2-heptanone, isoamyl acetate, propylene carbonate and tetrahydrofuran, etc.In one embodiment of the present invention, the alcohol organic solvent is more preferably one or more selected from isopropyl alcohol, propanol, butanol and hexyl alcohol. Isopropyl alcohol is the most suitable in the present invention.

[0047] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it is obvious to those skilled in the art that these embodiments are only provided for the purpose of more specifically describing the present invention, and the scope of the present invention is not limited by these embodiments.

[0048] As used in this specification, “comprises” and / or “comprising” are used in a meaning that does not exclude the existence or addition of the mentioned components, steps, actions and / or one or more other components, steps, actions and / or components other than the above components.

[0049] "Refined" as used in this specification means to purify a substance by removing impurities, but does not mean 100% removal, and may refer to a fluid having a substance content of at least 70% by weight, preferably 90% by weight, more preferably 95% by weight or 99% by weight after passing through a dehydration or refining mechanism. In the present invention, the so-called "refined organic solvent" may refer to a state in which organic impurities and / or metal impurities have been removed, and may be at a level of 99.999% or more.

[0050] A method for purifying an organic solvent according to an embodiment of the present invention includes: (a) supplying an organic solvent to a distillation tower 120 to perform distillation.

[0051] Figure 1 The figure shows a process diagram of a method for refining an organic solvent according to an embodiment of the present invention. The refining tower 100 of the present invention may include one or more of a raw material tank 110, a drying bed 111, a distillation tower 120, a reboiler 121, a reflux tank 122, a side discharge stream 130, an impurity discharge tank 140 and / or a product tank 150, and preferably includes all of them.

[0052] The method for purifying an organic solvent according to an embodiment of the present invention may include, as an initial step, a step of feeding an organic solvent raw material through a raw material tank 110 before (a) feeding the organic solvent to a distillation tower 120 to perform distillation. The step of feeding the organic solvent raw material through the raw material tank 110 is not particularly limited, and the organic solvent raw material may be fed at a flow rate of 500 kg / hr to 6,500 kg / hr.

[0053] The present invention may further include a step of removing the water contained in the organic solvent before the above-mentioned step (a) and after the step of adding the organic solvent raw material through the raw material tank 110. The organic solvent raw material added through the raw material tank 110 can improve the refining efficiency by removing the water contained in the organic solvent in advance in the drying bed part 111 before supplying it to the distillation tower 120. At this time, the method for removing water, that is, the dehydration process, can use methods known in the art without limitation, for example, azeotropic distillation, extractive distillation, and molecular sieve dehydration, etc., but is not limited thereto. In one embodiment of the present invention, when the above-mentioned molecular sieve dehydration method is applied, zeolite is preferably used.

[0054] The organic solvent from which water has been removed in the drying bed 111 flows into the distillation tower 120 to implement step (a). Step (a) may be a step of fractionating impurities using boiling point differences. The distillation tower 120 of the present invention is characterized by being connected to a side discharge stream 130. Specifically, Figure 1 As shown, it can be connected to the lower end of the distillation tower 120. In this case, relatively high boiling point organic impurities and / or metal impurities can be discharged together with a part of the organic solvent to the impurity discharge tank 140. In addition, when the discharge stream is connected to the upper end, relatively low boiling point organic impurities can be separated from the raw material.

[0055] In one embodiment of the present invention, the impurities may be substances having a boiling point higher than or the same as that of the organic solvent, including organic impurities and metal impurities.

[0056] The above-mentioned organic impurities are the largest source of contamination in the residues during the semiconductor device manufacturing process. They have hydrophobic surface properties, which greatly reduce the cleaning effect. They may cause a micro-mask effect during the process, and when they are not removed and remain, they may hinder the adhesion of the evaporated film.

[0057] Representative examples of the metal impurities include iron (Fe), chromium (Cr), nickel (Ni) and / or copper (Cu). 11 ~10 13 atoms / cm 2The level can also cause substrate contamination, which can be directly combined through the charge exchange between the silicon substrate and the metal ions, or be contaminated by metal impurities when an oxide film is formed on the surface of the substrate. In one embodiment of the present invention, the content of one or more metals among iron (Fe), chromium (Cr), nickel (Ni) and copper (Cu) contained in the organic solvent can be reduced to less than 30% of the raw material. Preferably, the iron (Fe), chromium (Cr), nickel (Ni) and / or copper (Cu) contained in the organic solvent refined according to the present invention can be a concentration of less than 5 ppt, more preferably a concentration of less than 3 ppt, and most preferably a concentration of less than 2 ppt.

[0058] Specifically, the impurities to be discharged through the side discharge stream 130 connected to the lower end of the distillation tower 120 may include, for example, one or more selected from n-propanol, 2-pentanone, 4-methyl-2-pentanone, 2-butanol, isopropyl acetate, nonanaldehyde, decanaldehyde, t-amyl alcohol, diacetone alcohol, and metal impurities.

[0059] The distillation tower 120 may be Figure 1 As shown, it is composed of a distillation tower. In order to improve the purity of the final organic solvent product, more than two distillation towers can also be configured in parallel. In addition, it can also be a multi-walled distillation (Multi-walled distillation) or a dividing-wall column (Dividing-wall columns) that realizes more than two distillations in one tower, but it is not limited to this.

[0060] The method for purifying an organic solvent according to an embodiment of the present invention comprises: (b) discharging a portion of the organic solvent containing impurities through a side discharge stream 130 connected to a lower end of a distillation tower 120 .

[0061] The impurities separated in the distillation tower 120 can be discharged to the impurity discharge tank 140 through the side discharge flow 130 together with a part of the organic solvent. In the present invention, it has been experimentally confirmed that at this time, a part of the organic solvent containing impurities is discharged through the side discharge flow 130 at a flow rate of 0.5 to 10% of the input flow rate of the organic solvent supplied to the distillation tower in the above step (a), preferably at a flow rate of 1.0 to 10% of the input flow rate of the organic solvent supplied to the raw material tank 110, thereby improving the purity of the organic solvent after the final purification. Specifically, the organic impurities such as acetone and / or metal impurities contained in the organic solvent after the final purification can be effectively controlled. When the discharge flow rate is lower than the above range, the purity is not appropriate even after the purification is completed. If the discharge flow rate is higher than 10%, the value of the impurities increases, resulting in a decrease in the product yield, and thus the inherent ability of the organic solvent is reduced. For example, for a cleaning liquid, the cleaning performance is reduced, and for a semiconductor cleaning liquid, wafer defects are induced.

[0062] Furthermore, the discharge in the step (b) is carried out as a continuous process, which has a very excellent advantage in reducing organic impurities, especially n-propanol (n-Propyl Alcohol), compared with a periodic discharge process.

[0063] The method for purifying an organic solvent of the present invention may further include: a step of liquefying the organic solvent distilled by the distillation tower 120 in the above step (a) through a condenser (not shown). When two or more condensers are connected in parallel, there is an advantage in the process that the organic solvent that has not been condensed in the primary condenser can be condensed again by condensers of two or more stages, thereby preventing loss.

[0064] After the above step (a) and before the step (b), the method may further include the step of re-vaporizing the liquefied impurities discharged from the lower end of the distillation tower. Figure 1 This is a step performed in the reboiler 121. Since it is difficult to completely separate impurities by a single distillation, a portion of the organic solvent containing impurities is returned to the distillation column 120 again to repeat vaporization and liquefaction, thereby performing redistillation. At this time, a method known in the art can be applied without limitation, but in one embodiment of the present invention, a heat exchange method (thermosyphon reboiler) using density difference of steam heat is suitable.

[0065] The method for refining an organic solvent of the present invention may further include: a step of refluxing the organic solvent distilled in the distillation tower 120 through the above step (a) from the reflux tank 122. The organic solvent refluxed from the reflux tank 122 is subjected to a redistillation process in the distillation tower, thereby obtaining an organic solvent with a higher purity. In addition, the purity of the organic solvent repeatedly distilled in the reflux tank 122 can be tested and then sent to the product tank 150, thereby obtaining a purified organic solvent with a higher purity.

[0066] <Organic solvents and storage methods for organic solvents>

[0067] The scope of the present invention includes an organic solvent purified by the method for purifying an organic solvent of the present invention and a method for storing the organic solvent. The organic solvent and the method for storing the organic solvent of the present invention include, without limitation, the contents described in the method for purifying an organic solvent.

[0068] Specifically, in the organic solvent purified according to the present invention, the content of one or more of n-propanol (n-Propyl Alcohol), 2-pentanone (2-Pentanone), 4-methyl-2-pentanone (4-Methyl-2-Pentanone), 2-butanol (2-Butanol), isopropyl acetate (Isopropyl Acetate), nonanaldehyde (Nonanaldehyde), decanaldehyde (Decanaldehyde), t-amyl alcohol (t-Amyl Alcohol) and diacetone alcohol (Diacetone Alcohol) can be 2 ppm or less, preferably less than 1 ppm, and the content of one or more of iron (Fe), chromium (Cr), nickel (Ni) and / or copper (Cu) can be 5 ppt or less, more preferably 3 ppt or less, and most preferably 2 ppt or less.

[0069] The method for purifying an organic solvent of the present invention may include a step of storing the organic solvent purified by the above method at a temperature lower than 35°C, preferably at a temperature lower than 30°C.

[0070] The organic solvent of the present invention may have an acetone content of 2 ppm or less, preferably less than 1 ppm, after being stored at a temperature below zero to below 35° C., preferably at a temperature below 30° C. for 7 days.

[0071] Below, experimental examples including specific embodiments and comparative examples are provided to help understand the present invention, but this is only an illustration of the present invention and does not limit the scope of the appended claims. For a person skilled in the art, it is obvious that various changes and modifications can be made to the embodiments within the scope and technical idea of ​​the present invention. Of course, such changes and modifications also fall within the scope of the appended claims.

[0072] Examples and Comparative Examples

[0073] Example: Continuous discharge of side discharge flow

[0074] 1. Effect of continuous discharge ratio based on side discharge flow

[0075] The following Tables 1 and 2 show that Figure 1 The method shown in the figure and the embodiment of the method for refining an organic solvent according to the present invention are the results of measuring the amount of impurities detected in the finally refined organic solvent based on the discharge amount in the side discharge stream 130 of the refining tower 100 during the purification of the raw material (main component: isopropyl alcohol). Specifically, in the following table, except for the "raw material level", the measurement of each impurity is carried out in the reflux tank 122 just before entering the product tank 150. The "raw material level" is the value obtained by measuring the impurities of the raw material before the organic solvent is purified according to the present invention.

[0076] (1) Determination of the discharge amount (%) of the side discharge flow

[0077] The side discharge flow discharge amount (%) is measured by the following method. Figure 1 In the process, the raw material (main component: isopropyl alcohol) is fed into the raw material tank 110 at a flow rate of 4100 to 4300 kg / hr (measured by a flow meter). Figure 1 The discharge flow rate in the side discharge stream 130 of the refining tower 100 was measured. The discharge rate of the side discharge stream was calculated according to the following formula and is shown in the following Tables 1 and 2.

[0078] Discharge rate of the side discharge flow (%) = [discharge flow rate in the side discharge flow 130 / input flow rate in the raw material tank 110] * 100

[0079] (2) Determination of organic impurities and metal impurities

[0080] The organic solvent (isopropyl alcohol) was purified by the above-mentioned embodiment. The organic solvent finally purified was collected in Figure 1The organic solvent in the reflux tank 122 was measured for organic impurities by GC method (GC-2010PLUS, Shimadzu Corporation), and for metal impurities by ICP-MSMS method (8900, Agilent Technologies Corporation), and the results are shown in Tables 1 and 2 below.

[0081] [Table 1]

[0082]

[0083] (Unit: ppm, metal system (Fe, Cr, Ni, Cu) unit: ppt)

[0084] [Table 2]

[0085]

[0086] (Unit: ppm, metal system (Fe, Cr, Ni, Cu) unit: ppt)

[0087] According to the experimental data in Tables 1 and 2, when the discharge amount of the side discharge flow is 1.0% or more, the results of less than 1 ppm are obtained in all organic impurities. For Fe, Cr, Ni and Cu, which are representative metals of stainless steel among the metal impurities, the results show that the organic solvent after purification is less than 30% relative to the impurities contained in the supplied organic solvent, and the discharge amount of the side discharge flow is 1.0% or more, and the results are 1 to 2 ppt, so that a final purified organic solvent with a good quality level can be obtained.

[0088] On the other hand, in the case of the discharge result of less than 0.5%, NPA (n-propyl alcohol) exceeds 1 ppm and the purity of the organic solvent decreases, and as a result, there is a possibility that defects may occur in the semiconductor process.

[0089] That is, the following effect was confirmed: generally, when the organic solvent containing impurities is discharged through the side discharge stream, the purity of the organic solvent finally obtained by purification is improved, but when the organic solvent containing impurities is discharged through the side discharge stream at a flow rate of preferably 0.5 to 10%, more preferably 1.0 to 10%, of the input flow rate of the organic solvent raw material supplied to the distillation column, the purity of the purified organic solvent is greatly improved.

[0090] 2. Relationship between the discharge volume in the side discharge flow and the production yield

[0091] Table 3 shows the production yield of the organic solvent obtained by the final purification based on the discharge amount (%) of the side discharge stream measured above.

[0092] [Table 3]

[0093] Side discharge flow discharge (%) Production yield (%) 1 99 2 98 3 97 4 96 5 95 6 94 7 93 8 92 9 91 10 90 11 89

[0094] Since the above production yield is directly related to product quality and manufacturing cost, it is important to reasonably set the discharge amount of the side discharge stream. The production yield refers to the value obtained by subtracting the discharge amount (%) in the side discharge stream from the total input flow rate of the organic solvent supplied to the entire refining tower as 100%. According to the experimental data in Table 3 above, if the discharge amount of the side discharge stream exceeds 10%, the production yield drops to less than 90%, which is not appropriate.

[0095] 3. Acetone content of purified organic solvent at different storage temperatures

[0096] Table 4 below shows the results of confirming the amount of acetone detected at different temperatures after sealing the organic solvent purified in the embodiment of the method for purifying an organic solvent according to the present invention in a 50 ml brown glass bottle and placing it in a temperature-maintaining device for 7 days. "Just purified" is the result of measuring the organic solvent immediately after the purification process according to the embodiment of the method for purifying an organic solvent according to the present invention at room temperature (about 25°C).

[0097] [Table 4]

[0098]

[0099] According to the experimental data in Table 4 above, the test results at different storage temperatures confirm that the data at room temperature remain unchanged at temperatures below zero and below 30°C, but once it is greater than 35°C, the acetone value immediately increases. In addition, if it is inferred that the acetone values ​​at 40°C and 50°C are higher than those at 35°C, it can be seen that high temperature energy promotes the regeneration of acetone. That is, it can be confirmed that the organic solvent purified according to the present invention is suitable for storage at a temperature below 35°C, preferably below 30°C.

[0100] 4. Acetone content of the purified organic solvent when stored at 40°C for a long time

[0101] The acetone content trend was confirmed by long-term evaluation at 40°C, which is greater than the appropriate temperature condition, and is shown in Table 5 below. The organic solvent obtained by refining according to the embodiment of the organic solvent refining method of the present invention was filled into an ISO tank lorry, kept at 40°C for long-term storage, and evaluated. The organic solvent was collected in a 50ml brown glass bottle and sealed, and then moved to the analysis room for analysis. The appropriate environmental conditions of the analysis room are a temperature of 15 to 30°C and a humidity of 30 to 60%. "Same-day measurement" is the result of the immediate measurement of the organic solvent after the refining process.

[0102] [Table 5]

[0103] distinguish Acetone(ppm) Same day measurement <1 Day 7 60.2 Day 14 60.5 Day 21 61.3 Day 28 60.0

[0104] According to the experimental data in Table 5, it can be confirmed that the temporarily increased acetone has a tendency to be maintained. That is, since the amount of acetone regenerated at different temperatures is constant, it can be said that long-term storage does not have a significant impact on the amount of acetone generated. For example, according to the experimental data, the amount of acetone generated at 40°C is about 60ppm.

[0105] Comparative example: Cyclic discharge of side discharge flow

[0106] In the method for purifying an organic solvent of the present invention, purification of the organic solvent was carried out in the same manner as in the above-mentioned Example, except that the discharge from the side discharge stream was performed periodically in cycles of 12 hours, 1 day, and 3 days instead of being discharged continuously.

[0107] For the organic solvent (isopropyl alcohol, Iso Propyl Alcohol) purified by side discharge at different cycles and finally purified, the contents of representative high boiling point impurity NPA (n-propanol, n-Propyl Alcohol) and low boiling point impurity acetone (Acetone) in the organic solvent were measured at each time period shown in the following Table 6, and are shown in the following Table 6.

[0108] [Table 6]

[0109]

[0110] (Unit: ppm)

[0111] According to the experimental data in Table 6, NPA (n-Propyl Alcohol) shows a narrow effect at the beginning of the cycle discharge, but for acetone, as the cycle becomes longer, the amount generated increases, and since it is a low-boiling impurity, it shows a continuous increase. That is, the biggest problem with the cycle discharge is that acetone will increase due to heat, thereby causing the concentration to increase exponentially. Therefore, it can be confirmed that when performing the process of the organic solvent purification method according to the present invention, continuous and frequent discharge is more conducive to improving the purity of the final product.

Claims

1. A method for refining an organic solvent, characterized in that: include: (a) supplying an organic solvent to a distillation column to perform distillation; as well as (b) a step of discharging a portion of the organic solvent containing impurities through a side discharge stream connected to the lower end of the distillation tower, In the discharge in the step (b), the organic solvent is discharged at a flow rate of 0.5 to 10% of the flow rate of the organic solvent supplied to the distillation tower in the step (a).

2. The method for purifying an organic solvent according to claim 1, wherein the organic solvent is an alcohol-based organic solvent.

3. The method for purifying an organic solvent according to claim 2, wherein the organic solvent is at least one selected from the group consisting of isopropanol, propanol, butanol and hexanol. 4 . The method for purifying an organic solvent according to claim 1 , wherein the impurity is a substance having a boiling point higher than or the same as that of the organic solvent.

5. The method for purifying an organic solvent according to claim 4, wherein the impurities include one or more selected from the group consisting of n-propanol, 2-pentanone, 4-methyl-2-pentanone, 2-butanol, isopropyl acetate, nonanal, decanal, tert-amyl alcohol, diacetone alcohol and metal impurities.

6. The method for purifying an organic solvent according to claim 1, wherein the discharge in the step (b) is carried out at a flow rate of 1.0 to 10% of the flow rate of the organic solvent supplied to the distillation tower in the step (a).

7. The method for purifying an organic solvent according to claim 1, wherein the discharge in step (b) is performed as a continuous process. 8 . The method for purifying an organic solvent according to claim 1 , wherein the content of one or more metals selected from the group consisting of iron (Fe), chromium (Cr), nickel (Ni) and copper (Cu) contained in the organic solvent is reduced to 30% or less.

9. The method for purifying an organic solvent according to claim 1, further comprising: A step of storing the purified organic solvent at a temperature lower than 35°C.

10. The method for purifying an organic solvent according to claim 9, further comprising: A step of storing the purified organic solvent at a temperature of 30° C. or lower.

11. The method for purifying an organic solvent according to claim 1, further comprising one or more of the following steps: Prior to step (a), a step of removing water contained in the organic solvent; After step (a) and before step (b), a step of re-vaporizing the liquefied impurities discharged from the lower end of the distillation tower; After the step (a), a step of liquefying the distilled organic solvent by a condenser; and After the step (a), a step of refluxing the organic solvent distilled out in the distillation tower.

12. An organic solvent, wherein The content of one or more of n-propanol, 2-pentanone, 4-methyl-2-pentanone, 2-butanol, isopropyl acetate, nonanal, decanal, tert-amyl alcohol and diacetone alcohol is a concentration below 2 ppm, and the content of one or more of iron Fe, chromium Cr, nickel Ni and copper Cu is a concentration below 5 ppt.

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