阅读说明：本技术 废n-甲基-2-吡咯烷酮混合液的纯化方法 (Purification method of waste N-methyl-2-pyrrolidone mixed liquor ) 是由 沈成元 于 2020-07-07 设计创作，主要内容包括：本发明涉及一种废N-甲基-2-吡咯烷酮(下称为NMP)混合液的纯化方法,更详细地,涉及一种利用碱来纯化废NMP混合液的方法。根据本发明,在废NMP混合液中适用碱来同时去除NMS及GBL,从而可回收高纯度的NMP。(The present invention relates to a method for purifying a waste N-methyl-2-pyrrolidone (hereinafter, referred to as NMP) mixed solution, and more particularly, to a method for purifying a waste NMP mixed solution using an alkali. According to the present invention, NMS and GBL are simultaneously removed from a waste NMP mixture by using an alkali, thereby recovering NMP having a high purity.)

1. A method for purifying a waste N-methyl-2-pyrrolidone mixed solution by adding an alkali to a waste NMP mixed solution containing N-methylsuccinimide (NMS) and gamma-butyrolactone (GBL) as by-products of N-methyl-2-pyrrolidone (NMP) to simultaneously remove NMS and GBL,

the base is NaBH4 (hereinafter SBH),

the NMS reacts with the SBH to convert to 5-hydroxy-N-methyl-2-pyrrolidone, and the GBL reacts with the SBH to convert to 1, 4-butanediol.

2. The method for purifying a waste NMP mixed liquor according to claim 1,

the SBH is added in an amount of 0.05 to 0.10 wt% based on the total weight of the waste NMP mixed solution.

3. The method for purifying a waste NMP mixed liquor according to claim 2,

the water is added in a content of 5 to 20 wt% with respect to the total weight of the whole reactants,

the reaction temperature is 100-150 ℃, and the reaction time is 10-60 minutes.

4. The method for purifying a waste NMP mixed liquor according to claim 3,

the SBH was added dissolved in NaOH at a concentration of 10% (w/v).

5. The method for purifying a waste NMP mixed liquor according to claim 1,

the 5-hydroxy-N-methyl-2-pyrrolidone is formed as the following reaction formula 1,

the 1, 4-butanediol is formed in the following reaction formula 2:

[ reaction formula 1]

[ reaction formula 2]

6. The method for purifying a waste NMP mixed liquor according to claim 1,

the waste NMP mixed solution is derived from waste liquid used in a secondary battery preparation process.

Technical Field

The present invention relates to a method for purifying a waste N-methyl-2-pyrrolidone (hereinafter, referred to as NMP) mixed solution, and more particularly, to a method for purifying a waste NMP mixed solution using an alkali.

Background

N-methyl-2-pyrrolidone (NMP) is an organic solvent with low viscosity, colorless, non-toxic, and excellent heat resistance. NMP is a highly polar solvent with good chemical stability and therefore is very useful for a variety of chemical reactions that require an inert medium.

With the increasing environmental regulations, NMP is an increasingly demanded product as an environmentally friendly nontoxic product in the fields of solvents for polymer polymerization and processing, solvents for manufacturing paints, metal surface cleaning agents, solvents for synthesizing and purifying pharmaceuticals, processing solvents for semiconductors and electronic materials, solvents for manufacturing lithium secondary batteries, and the like.

In particular, NMP may be included in the binder as a solvent for forming an active material in the manufacturing process of the anode and the cathode in the manufacturing process of the secondary battery. NMP can be used as a dispersion solvent in the active material mixing tank, and can be recovered in a vapor state in the drying step after the electrode is formed. At this time, the waste NMP may contain about 30 wt% of moisture.

In addition, when the waste NMP used in the process is recovered and reused, the method not only has economic benefit, but also has great effect of reducing the discharge of environmental pollution sources. Therefore, studies relating to a method of purifying NMP of high purity by purifying the waste NMP used in the end are actively being conducted.

In the synthesis process of NMP, a certain amount of GBL (gamma-butyrolactone) remains, and in the purification process by distillation, the boiling point of NMP (boiling point 202 ℃) is very close to that of GBL (boiling point 204 ℃) which is an impurity, so that GBL is difficult to remove, and therefore, all NMP products contain about 200 to 400wtppm of GBL.

Further, NMP is oxidized by oxygen in the air during storage, transportation and use to generate a large amount of NMS (N-methylsuccinimide) having a boiling point of 234 ℃ C. so that NMP products contain a large amount of NMS and waste NMP may contain NMS of 200 to 500wtppm or more. Although NMS has a boiling point that is quite different from that of NMP, it has a problem that NMS cannot be completely removed in the process of purifying a waste NMP mixture by distillation. In particular, in industries requiring NMP of 99.9 wt% or more as a processing solvent for semiconductor and electronic materials and a solvent for lithium battery production, removal of NMS, GBL, and the like is required, but a solution thereof has not been proposed at present.

Further, in the NMP product and the waste NMP mixture, since about 300 to 350wtppm of 1,3-DMP (1,3-Dimethyl-2-pyrrolidone) and 1,4-DMP (1,4-Dimethyl-2-pyrrolidone) that have not been removed by fractionation are usually left in the waste NMP product and the waste NMP mixture, respectively, it is necessary to remove NMS and GBL in order to purify and recover high-purity NMP from the waste NMP mixture.

Korean laid-open patent No. 10-2015-0085065 discloses a method of purifying and reusing N-alkylpyrrolidone to be purified by adding an alkaline compound thereto and performing distillation, and published patent No. 10-2018-0069284 discloses a method of purifying high-purity NMP by adding an alkaline compound to a waste NMP mixture to simultaneously remove NM3P (N-methyl-3-pyrrolin-2-one) and NMs (N-methylsuccinimide), and US2,964,535 discloses a method of removing GBL as an impurity contained in NMP.

However, a method of purifying a waste NMP mixture by simultaneously removing NMS (N-methylsuccinimide) and GBL (gamma-butyrolactone), which are impurities remaining in the waste NMP mixture, has not been proposed.

[ Prior art documents ]

1. Korean laid-open patent publication No. 10-2015-

2. Korean laid-open patent publication No. 10-2018-0069284(2018.06.25. publication)

3. United states patent 2,964,535(1960.12.13 grant)

Disclosure of Invention

Solves the technical problem

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for recovering high-purity NMP by applying a fractionation step after NMS and GBL as impurities remaining in a waste NMP mixture are simultaneously removed.

Technical scheme

In one embodiment of the present invention, there is provided a method for purifying a waste NMP mixture by simultaneously removing N-methylsuccinimide (N-methyluccimide) and GBL (gamma-Butyrolactone), which are present in the waste NMP mixture or are generated as a by-product of NMP during purification, by adding a base, which may be SBH (NaBH) to the waste NMP mixture₄)。

In another embodiment of the present invention, the SBH may be added in an amount of 0.05 to 0.10 wt% based on the total weight of the waste NMP mixture.

In a method for purifying a waste NMP mixed solution according to still another embodiment of the present invention, water is added in an amount of 5 to 20 wt% based on the total weight of the entire reactants, the reaction temperature is 100 to 150 ℃, and the reaction time may be 10 to 60 minutes.

In a method of purifying a waste NMP mixture according to still another embodiment of the present invention, the SBH may be added in a form of being dissolved in NaOH having a concentration of 10% (w/v).

Effects of the invention

A method for purifying waste NMP according to the present invention can simultaneously remove NMS and GBL and recover high-purity NMP by using a suitable base.

Drawings

Fig. 1 shows the results of GC (Gas Chromatography) analysis of a mixture of waste NMP containing NMS and GBL as impurities.

Figure 2 is the results of a GC analysis of the spent NMP mixture after SBH treatment.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the description of the constituent elements of the present invention, terms such as 1 st, 2 nd, 3 rd, 1 st, 2 nd, A, B th, (a), (b) and the like can be used. These terms are only used to distinguish one constituent element from another constituent element, and do not limit the nature, order, sequence, and the like of the corresponding constituent elements. In the description of the present invention, a detailed description of a related known structure or function will be omitted when it is judged that the detailed description may obscure the gist of the present invention.

Unless otherwise defined, all terms used in the present specification have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, and when conflicting with a term used in the present specification, the definition used in the present specification follows. In the entire specification, unless specifically stated to the contrary, when a part "includes" a certain component, it means that the other component is included but not excluded.

In one specific example of an embodiment of the present invention, there is provided a method for purifying a waste NMP mixture, in which N-Methylsuccinimide (N-methyluccinimide) and GBL (gamma-Butyrolactone), which are by-products of NMP remaining in the waste NMP mixture, are simultaneously removed by adding an alkali to the waste NMP mixture.

As is clear from fig. 1, the waste NMP mixture contains N-Methylsuccinimide (N-Methylsuccinimide) and GBL (gamma-Butyrolactone) as impurities. FIG. 1 shows the results of GC (Gas Chromatography) analysis of a waste NMP mixture, and referring to FIG. 1, peaks were observed in N-Methylsuccinimide (N-Methylsuccinimide) and GBL (gamma-Butyrolactone)).

According to the present invention, NMS and GBL as impurities can be completely removed at the same time by reacting the waste NMP mixture with a reducing agent such as SBH. That is, NMS (boiling point: 234 ℃ C.) contained in the waste NMP is reacted with SBH and converted into 5-hydroxy-N-methyl-2-pyrrolidone (boiling point: 276 ℃ C.) as shown in the following reaction scheme 1, and GBL (boiling point: 204 ℃ C.) contained in the waste NMP is reacted with SBH and converted into 1, 4-butanediol (boiling point: 230 ℃ C.) as shown in the following reaction scheme 2.

NMP has a boiling point of 202 ℃ similar to GBL. Therefore, when directly fractionating waste NMP, it is difficult to remove GBL, and when reacting with SBH, like the present invention, it is converted into high boiling point materials compared to NMP, so that the converted materials can be fractionated and removed. This can be confirmed by fig. 2.

Fig. 2 shows the results of GC analysis after SBH treatment of the waste NMP mixture, and unlike fig. 1, no peak of GBL or NMS was observed.

[ reaction formula 1]

[ reaction formula 2]

In addition, in the method for purifying a waste NMP mixed solution according to an embodiment of the present invention, the base may be SBH (Sodium borohydrate, NaBH)₄))。

Generally, the reduction reaction in the organic chemical reaction is a reaction in which hydrogen is bonded or the oxidation state is decreased, and a reducing agent causing the reduction reaction includes Metal hydrides (Metal hydrides) which directly supply Hydride anions (H —, Hydride), and typical examples thereof include Lithium Aluminum Hydride (LAH), LiAlH Hydride₄) With Sodium Borohydride (Sodium borohydrate (SBH), NaBH₄)。

Among these LAH and SBH, LAH has a far stronger reducing ability than SBH, and generally converts a hydroxyl group of all Carbonyl (C ═ O) compounds described below into a methylene group (CH 2). However, since SBH is weaker than LAH in reducing ability, it is known that SBH can be reduced to only ketones in general in the following order of compounds.

It is known that this reduction reaction is caused by the hydride ion as a negative ion attacking C, which is a part of the positively charged hydroxyl group in C ═ O, and starting from the Ester (Ester), part of C becomes weakly positive due to electron-pushing by O adjacent to C of C ═ O due to the Inductive Effect (induced Effect), so that SBH having a weak reducing ability cannot cause the reduction reaction.

However, NMS can pull electrons from both sides of N-methyl group with C ═ O on both sides, so that C of one side of C ═ O becomes more positive and thus the reaction is easy to proceed, but NMP has C ═ O on only one side, and thus it is considered that the reaction cannot be caused.

In addition, GBL is assumed to form a stable structure as the pentagonal structure is cleaved (the Strain (Strain)) due to the Cyclic Ester (Lactone) being more reactive than the amide, and to be able to react even though it is an Ester.

In a method of purifying a waste NMP mixture according to still another embodiment of the present invention, the SBH may be added in an amount of 0.05 to 0.10 wt% with respect to the total weight of the waste NMP mixture. When the added SBH content is out of the range, it may be impossible to completely remove both NMS and GBL contained in the waste NMP mixture.

In a method for purifying a waste NMP mixed solution according to still another embodiment of the present invention, water is added in an amount of 5 to 20 wt% based on the total weight of the entire reactants, the reaction temperature is 100 to 150 ℃, and the reaction time may be 10 to 60 minutes. When the reaction conditions are out of the range, NMS and GBL contained in the waste NMP mixture may not be completely removed at the same time.

In a method of purifying a waste NMP mixture according to still another embodiment of the present invention, the SBH may be added in a form of being dissolved in NaOH having a concentration of 10% (w/v). When the reaction conditions are out of the range, NMS and GBL contained in the waste NMP mixture may not be completely removed at the same time.

Hereinafter, an example of a method for purifying a waste NMP mixed solution according to an embodiment of the present invention will be described. The following examples are merely illustrative of the present invention, and the scope of the present invention is not limited to these examples.

Examples and comparative examples

< example 1> to < example 10>

200g of a waste NMP mixture containing 200 to 500wtppm NMS and 200 to 400wtppm GBL based on the total weight of the waste NMP mixture is put into a 500mL round-bottom flask, and a solution prepared by dissolving SBH in a 10% (w/v) NaOH aqueous solution is put into the waste NMP mixture while stirring at 200 to 250rpm at 25 to 150 ℃. In this case, the composition of the waste liquid, the amount of SBH charged, the reaction temperature, and the like are as shown in Table 1 below. In table 1 below, the input amount of SBH is the input amount relative to the total weight of the waste liquid mixture.

< comparative example 1> to < comparative example 11>

200g of a waste NMP mixture containing 200 to 500wtppm NMS and 200 to 400wtppm GBL based on the total weight of the waste NMP mixture is put into a 500mL round-bottom flask, and then 10% (w/v) NaOH aqueous solution is put into the waste NMP mixture while stirring at 200 to 250rpm at 25 to 150 ℃. In this case, the composition of the waste liquid, the amount of SBH charged, the reaction temperature, and the like are as shown in Table 1 below.

As a result of carrying out the reactions according to examples 1 to 10 and comparative examples 1 to 11, the composition of the waste liquid after the reaction is as shown in Table 1 below. In table 1, the contents of the respective components of the waste liquid, the comparative example, and the example are the contents of organic substances other than water.

[ Table 1]

As can be seen from table 1, when a waste solution containing about 300wtppm of NMS and about 250wtppm of GBL was used, GBL and NMS remained in the case of the comparative example, whereas GBL and NMS were not observed at all in the case of the example of the present invention.

Therefore, according to the present invention, it is found that NMS and GBL can be completely removed from the waste NMP mixture at the same time when the SBH content is 0.05 to 0.10 wt% under the reaction conditions of 5 to 20 wt% of water, 100 to 150 ℃ of reaction temperature, and 10 to 60 minutes of reaction time.

Furthermore, from the results of comparative examples 1 to 11 in table 1, it is understood that NMS and GBL cannot be completely removed from the waste NMP mixture at the same time when the experimental conditions of examples 1 to 10 are out of the range.

< example 11>

This is the case where a 10% (w/v) aqueous NaOH solution in which SBH was dissolved was treated at a reaction temperature of 100 ℃ with respect to a waste NMP containing 0.12 wt% of NMS and about 270wtppm of GBL.

< comparative example 12> to < comparative example 14>

The procedure was repeated in the same manner as in example 11, except that a 10% (w/v) aqueous NaOH solution in which SBH was not dissolved was used.

In the treatment of waste liquid according to example 11 and comparative examples 12 to 14, the composition of the mixture after the treatment is as shown in the following Table 2.

[ Table 2]

As can be seen from table 2, in comparative examples 12 and 13, NMS and GBL were hardly removed from the waste liquid, and in comparative example 14, NMS and GBL were removed much more than in comparative examples 12 and 13, but were not completely removed. On the contrary, in example 11 of the present invention, it was confirmed that NMS and GBL in the waste NMP mixture were completely removed.

< example 12> fractionation Using distillation column

In examples 7 and 12, the results of applying SBH to a waste NMP mixture containing NMS and GBL to completely remove NMS and GBL at the same time to obtain a waste NMP mixture, fractionating the waste NMP mixture using a 30-layer Sieve Tray (Sieve Tray) distillation column of a 5L scale Pilot (Pilot) under a pressure of 40 to 100mmHg to remove 0 to 15% of moisture and low boiling impurities and recover 15 to 80% of purified NMP are shown in table 3 below. In table 3 below, the contents of the waste liquid and each component of the examples are the contents in organic substances other than water.

[ Table 3]

As can be seen from table 3, in the case of examples 7 and 12 of the present invention, both NMS and GBL were not present in the mixture obtained by the fractional distillation. Therefore, according to the present invention, if the waste NMP mixture is treated with SBH and then fractionated, impurities such as GBL or NMS can be removed.

The above description is merely exemplary, and various modifications can be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present specification are not intended to limit the present invention, but to illustrate the present invention, and the spirit and scope of the present invention are not limited by such embodiments. The scope of the invention should be construed in accordance with the appended claims, and all technical equivalents thereof should be construed as being included in the scope of the invention.

Cross reference to related patent applications

The present patent application claims priority to patent application No. 10-2019 § 0082112, filed in korea on year 2019, 07/08, according to us patent laws 119 to 121, 365 (35u.s.c § 119 to 121, § 365), the entire content of which is incorporated herein by reference. If priority is claimed in this patent application for the same reason in other countries than the united states, the entire contents of the patent application are incorporated by reference.