WO2022019507A1 - Method for recovering carboxylic acids and amide compounds by using pressure swing distillation - Google Patents

Abstract

The present invention relates to a method for recovering carboxylic acids and amide compounds through separation and, especially, to a method for recovering a mixture of acetic acid and dimethyl formamide (DMF) contained in a waste solvent through separation, wherein pressure swing distillation using a difference in azeotropic composition of DMF and acetic acid between a high-vacuum condition and a normal pressure condition is employed. The maximum-temperature azeotropic mixture of acetic acid and DMF cannot be separated by simple distillation, and thus after confirming a sufficient difference in acetic acid proportion between a vacuum azeotropic composition and a normal-pressure azeotropic composition of acetic acid-DMF, a process scheme capable of separating and recovering DMF and acetic acid from the waste solvent by applying pressure swing distillation was derived. Compared with a method of recovering DMF after the neutralization of acetic acid with caustic soda, the present invention has advantages in that no caustic soda is used, no salt wastewater is generated, and no odor is caused by DMF-derived dimethyl amine produced during the use of caustic soda. Furthermore, compared with the method using caustic soda neutralization, the recovery rate of DMF is high and acetic acid recovered as a byproduct can also be utilized as a raw material for preparing other ester compounds.

Description

Method for Recovery of Carboxylic Acid and Amide Compounds Using Pressure Swing Distillation

The present invention relates to a method for recovering useful components from a waste solvent, and more particularly, to a method for recovering each component by using the difference in the azeotropic composition of a carboxylic acid and an amide compound under high vacuum conditions and atmospheric pressure conditions.

Typical components of the components included in the waste solvent generated during the manufacture of polyimide films for semiconductors and displays and the composition of each component are shown in Table 1 below.

	water	acetic acid (Acetic Acid)	3MP (3-methylpyridine)	DMF (Dimethylformamide)
boiling point, °C	100	118	143-144	153
composition ratio, %	10	15	2	73

Acetic acid and DMF form an azeotropic mixture at maximum temperature, and according to literature, the azeotropic temperature is 159 °C and the azeotropic composition is 26% acetic acid and 74% DMF. 3MP can be removed, and a mixture of 17% acetic acid and 83% DMF can be obtained as the bottom of the tower.

When this is put back into a conventional distillation column, a portion of DMF is recovered to the top, but an azeotropic mixture of 26% acetic acid and 74% DMF is obtained at the bottom of the column. Even if the azeotrope obtained in this way is put back into a general distillation column, an azeotrope having the same composition is obtained at the top and bottom of the column, and separation is impossible.

Extractive distillation, azeotropic distillation, pressure swing distillation, etc. are suggested as a method for separating an azeotrope, and among these methods, an efficient method according to the characteristics of the azeotrope can be used to separate azeotropes. However, this choice is not possible in all these cases, and even if separation of the azeotrope is possible by the selected method, it may not be economical.

In particular, as a technique for separating acetic acid and DMF, Japanese Patent Laid-Open No. 2002-363150 proposes a method for separating acetic acid and dimethylformamide by using toluene as an azeotrope with acetic acid but not with dimethylformamide. In addition, Korean Patent Publication No. 10-2010-0130219 proposes a method of removing carboxylic acid from a solution containing tertiary amide by contacting a solution containing carboxylic acid and tertiary amide with an extraction medium containing trilaurylamine, and have. However, since the above-mentioned prior art requires a third component, economical efficiency is low, and the efficiency of the separation process is not sufficient, so a separation technology to supplement this is required.

The method for recovering the carboxylic acid and amide compound of the present invention has been devised to solve the above problems, and in consideration of the characteristics of the azeotrope of acetic acid and DMF, separation capable of effectively separating DMF from the azeotrope of acetic acid and DMF After selecting a method, based on the selected method, we intend to derive an efficient and economical process scheme that can recover acetic acid and DMF from waste solvents including acetic acid and DMF.

The present invention may also have the object of achieving these objects and other objects that can be easily derived by a person skilled in the art from the general description of the present specification in addition to the above clear objects.

In the method for recovering a carboxylic acid and an amide compound of the present invention, in order to achieve the above object, a mixture containing a carboxylic acid and an amide compound is put into a high vacuum distillation column, the amide compound is recovered through the top of the high vacuum distillation column, and the bottom of the high vacuum distillation column obtaining a mixture comprising a carboxylic acid and an amide compound having a first azeotropic composition (S11); The mixture containing the carboxylic acid and the amide compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered at the top of the atmospheric distillation column, and the mixture containing the carboxylic acid and the amide compound having the second azeotropic composition at the bottom of the atmospheric distillation column obtaining (S12); and a step (S13) of recirculating all or part of the mixture including the carboxylic acid and the amide compound having the second azeotropic composition into the high vacuum distillation column (S13).

And, the bottom pressure of the high vacuum distillation column may be 200 torr or less, 150 torr or less, or 100 torr or less.

And, the DMF recovered to the top of the high vacuum distillation column may have a purity of 97% or more, 98% or more, or 99% or more.

And, the bottom pressure of the atmospheric distillation column may be 700 to 800 torr, 720 to 780 torr, or 750 to 770 torr.

And, the acetic acid recovered to the top of the atmospheric distillation column may have a purity of 95% or more, 97% or more, or 98% or more.

In addition, 1 to 100 parts by weight, 50 to 99.99 parts by weight, 80 to 99.9, or 90 to 99 parts by weight may be recycled based on 100 parts by weight of the mixture including the carboxylic acid having the second azeotropic composition and the amide compound.

In addition, before the step S11,

may include a step (S10) of adding a waste solvent containing water, carboxylic acid, and an amide compound to the distillation column, separating water from the top of the distillation column, and obtaining a mixture containing the carboxylic acid and the amide compound with the bottom of the distillation column (S10); have.

In addition, the waste solvent further includes a pyridine-based compound, and the pyridine-based compound may be separated together with water at the top of the distillation column.

In addition, the pyridine-based compound may include 3-methylpyridine.

In addition, the carboxylic acid and the amide compound may form an azeotrope at maximum temperature when mixed.

In addition, the carboxylic acid may be acetic acid.

In addition, the amide compound may be N,N-dimethylformamide.

And, the carboxylic acid and the amide compound having the first azeotrope composition, based on a total of 100 parts by weight of the carboxylic acid and the amide compound having the first azeotropic composition, 30 to 40 parts by weight, 32 to 38 parts by weight, or 33 parts by weight of the carboxylic acid to 37 parts by weight.

In addition, the carboxylic acid and amide compound having the second azeotropic composition are used in an amount of 20 to 30 parts by weight, 22 to 29 parts by weight, or 24 parts by weight of the carboxylic acid based on 100 parts by weight of a total of 100 parts by weight of the carboxylic acid and amide compound having the second azeotropic composition. to 28 parts by weight.

In addition, the high vacuum distillation column may be a packing tower.

In addition, the atmospheric distillation column may be a packing tower.

And, the atmospheric distillation column may be provided with a forced circulation reboiler.

On the other hand, in the method for recovering a carboxylic acid and an amide compound according to the present invention, a mixture containing a carboxylic acid, an amide compound, and a quinoline-based compound is put into a high vacuum distillation column, the amide compound is recovered through the top of the high vacuum distillation column, and the bottom of the high vacuum distillation column is used obtaining a mixture including a carboxylic acid having a first azeotropic composition, an amide compound, and a quinoline-based compound (S21); The mixture containing the carboxylic acid, the amide compound, and the quinoline compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered at the top of the atmospheric distillation column, and the carboxylic acid and the amide having a second azeotropic composition at the bottom of the atmospheric distillation column obtaining a mixture comprising the compound, and a quinoline-based compound (S22); and a step (S23) of recirculating all or part of the mixture including the carboxylic acid having the second azeotropic composition, the amide compound, and the quinoline-based compound into the high vacuum distillation column (S23).

In addition, all or part of the mixture including the carboxylic acid and the amide compound having the second azeotropic composition, and the quinoline compound is added to a distillation column to remove the quinoline compound, and then added to the high vacuum distillation column (S24); may include more.

And, the quinoline-based compound may be recovered to the bottom of the distillation column.

In addition, before step S21, a waste solvent containing water, carboxylic acid, an amide compound, and a quinoline-based compound is added to the distillation column, water is separated at the top of the distillation column, and carboxylic acid, an amide compound, and a bottom of the distillation column It may include; obtaining a mixture containing a quinoline-based compound (S20).

And, the quinoline-based compound may be quinoline, methylquinoline, or 3-methylquinoline (3-methylquinoline).

In addition, the high vacuum distillation column may be a packing tower.

In addition, the atmospheric distillation column may be a packing tower.

And, the carboxylic acid may be acetic acid.

In addition, the amide compound may be N,N-dimethylformamide.

As a method for recovering DMF from an azeotropic mixture of acetic acid and DMF, as shown in FIG. 1, after neutralizing acetic acid with NaOH (caustic soda), water, 3MP, and DMF are distilled from the salt (Sodium Acetate) produced using a dryer. A recovery method has been introduced and used. This requires caustic soda cost and has disadvantages in that the DMF recovery rate due to the DMF contained in the salt remaining in the dryer is low.

In addition, it is known that wastewater containing sodium acetate is generated as much as the amount of DMF recovered, and since such salt wastewater has a high treatment cost per ton, it becomes the biggest cost burden. In addition, during the neutralization process of acetic acid using caustic soda, the odor caused by dimethylamine generated when DMF is hydrolyzed by NaOH may be a problem.

On the other hand, the present invention separates the azeotropic mixture of acetic acid and DMF by pressure swing distillation instead of the neutralization method of acetic acid using caustic soda. Severe dimethylamine is not generated.

In addition, when DMF is recovered by pressure swing distillation, a relatively high DMF recovery rate can be expected, and acetic acid obtained as a by-product can be utilized.

Therefore, when the pressure swing distillation is applied, it is expected that the process can be operated with a relatively small number of manpower because the process is simple as well as the effect of lowering the manufacturing cost.

1 shows a conventional DMF recovery method of neutralizing and removing acetic acid with caustic soda.

2 is a graph showing the composition according to the CLV of the overhead distillate in a batch distillation experiment (vacuum distillation) of a mixture of acetic acid and DMF.

3 is a graph showing the composition according to the CLV of the overhead distillate in a batch distillation experiment (atmospheric distillation) of a mixture of acetic acid and DMF.

4 is a graph showing the measured values of the azeotrope composition of acetic acid and DMF for each vacuum pressure.

5 shows a pressure swing distillation scheme of a mixture of acetic acid and DMF according to an embodiment of the present invention.

6 is a flowchart illustrating a method for recovering acetic acid and DMF using pressure swing distillation according to an embodiment of the present invention.

7 is a flowchart illustrating a method for recovering acetic acid and DMF using pressure swing distillation according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.

However, the present invention is not limited to the specific exemplary embodiments, since the following is merely a detailed description by exemplifying specific embodiments, and since the present invention may be variously changed and may have various forms. It should be understood that the present invention includes all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

In addition, in the following description, many specific details such as specific components are described, which are provided to help a more general understanding of the present invention, and it is common in the art that the present invention can be practiced without these specific details. It will be self-evident to those who have the knowledge of And, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

And, the terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Unless defined otherwise, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

In this application, the singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

In the present application, terms such as 'comprise', 'contain' or 'have' are intended to refer to the presence of a feature, component (or component), etc. described in the specification, but one or more other features or It does not mean that the component or the like is not present or cannot be added.

The present invention relates to a method for recovering a carboxylic acid and an amide compound for separating a carboxylic acid and an amide compound contained in a waste solvent generated during the manufacture of a polyimide film for semiconductors and displays, wherein the carboxylic acid and the amide compound forming an azeotrope are inputting the mixture containing the mixture into a high vacuum distillation column, recovering the amide compound to the top of the high vacuum distillation column, and obtaining a mixture of the carboxylic acid and the amide compound having a first azeotropic composition to the bottom of the high vacuum distillation column (S11); Putting a mixture of carboxylic acid and amide compound having the first azeotropic composition into an atmospheric distillation column, recovering carboxylic acid to the top of the atmospheric distillation column, and obtaining a mixture of carboxylic acid and amide compound having a second azeotropic composition to the bottom of the atmospheric distillation column ( S12); And it relates to a method for recovering a carboxylic acid and an amide compound, comprising a step (S13) of recycling all or a part of the mixture of the carboxylic acid and the amide compound having the second azeotropic composition into the high vacuum distillation column.

In the method for recovering the carboxylic acid and the amide compound according to the present invention, the carboxylic acid and the amide compound form an azeotropic mixture at maximum temperature, and thus provide a useful method for separating each component constituting the mixture. In particular, the carboxylic acid may be acetic acid, wherein the amide compound is an amide compound that forms an azeotropic mixture with acetic acid at maximum temperature. The amide compound may be a tertiary amide compound, and may be formamide, N,N-dimethylformamide, N,N-diethylformamide, or N-methyl-N-ethylformamide.

In particular, the present invention separates and recovers a mixture of Acetic Acid (AA) and N,N-dimethylformamide (DMF) contained in waste solvents generated during the manufacture of polyimide films for semiconductors and displays. As a method, it is characterized by using a pressure swing distillation using the difference in the azeotropic composition of DMF and acetic acid under high vacuum conditions and atmospheric pressure conditions.

The composition of an azeotropic mixture of acetic acid and N,N-dimethylformamide (DMF) is acetic acid 26%, DMF 74%, and the azeotrope temperature is 159 ° C. No literature on the composition could be found. Accordingly, the present inventor conducted an experiment to confirm the azeotropic composition of acetic acid and DMF under vacuum pressure conditions, and the azeotropic composition at 30 torr condition is 36% or more of acetic acid, compared to the azeotropic composition (26% of acetic acid) under atmospheric pressure conditions, It was confirmed that it was higher than 10%. Therefore, it was determined that separation of acetic acid and amide compound could be effectively achieved through pressure swing distillation using the difference in azeotrope between atmospheric pressure and vacuum.

5 schematically shows a method for recovering a carboxylic acid and an amide compound according to the present invention, wherein the maximum temperature azeotropic mixture (A + B) such as acetic acid-DMF is through pressure swing distillation using the difference in azeotropic composition between vacuum and atmospheric pressure. , DMF (A) from the top of the high vacuum distillation column 10, and acetic acid (B) from the top of the atmospheric distillation column 20 can be recovered. _{An azeotrope under vacuum conditions (A 1} +B ₁ ) can be obtained as the bottom of the high vacuum distillation column 10 , and an azeotrope under _{atmospheric pressure (A 2} +B ₂ ) can be obtained as the bottom of the atmospheric distillation column 20 . Therefore, according to the present invention, since the third component is not required for the separation of the two components, the cost can be reduced, and the wastewater by the third component is not generated, so wastewater treatment is unnecessary and environment-friendly. In addition, the recovery rate of the amide compound using the pressure swing distillation is very good.

Hereinafter, the detailed contents of each step are as follows.

First, a mixture containing a carboxylic acid and an amide compound is put into a high vacuum distillation column, the amide compound is recovered at the top of the high vacuum distillation column, and a mixture of a carboxylic acid and an amide compound having a first azeotropic composition is obtained at the bottom of the high vacuum distillation column.

At this time, the bottom pressure of the high vacuum distillation column may be 200 torr or less, 150 torr or less, or 100 torr or less. The azeotropic composition ratio under the pressure in the above range shows a sufficient difference from the azeotrope composition ratio under normal pressure, thereby enabling component separation by pressure swing distillation. The lower limit is not particularly limited, but the efficiency and economic feasibility of the process should be considered. In addition, the high vacuum distillation column may be a packing tower capable of minimizing the differential pressure between the top and the bottom in order to maintain the bottom pressure as low as possible.

A high-purity amide compound is recovered from the top of the high-vacuum distillation column, and it may have a purity of 97% or more, 98% or more, or 99% or more. A mixture containing a carboxylic acid having a first azeotropic composition and an amide compound is obtained at the bottom of the high vacuum distillation column. The carboxylic acid and amide compound having the first azeotropic composition is an azeotropic mixture under high vacuum conditions, and based on 100 parts by weight of the carboxylic acid and the amide compound having the first azeotropic composition, 30 to 40 parts by weight, 32 to 38 parts by weight of the carboxylic acid , or 33 to 37 parts by weight, in this case, the carboxylic acid is acetic acid and the component other than this may be composed of DMF.

Next, the mixture containing the carboxylic acid and the amide compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered at the top of the atmospheric distillation column, and the carboxylic acid and the amide compound having a second azeotropic composition are obtained at the bottom of the atmospheric distillation column. to obtain a mixture containing

At this time, the bottom pressure of the atmospheric distillation column may be 700 to 800 torr, 720 to 780 torr, or 750 to 770 torr, and may be about 760 torr. In addition, the atmospheric distillation column may be a packing tower capable of minimizing the differential pressure between the top and the bottom in order to minimize thermal decomposition of amide compounds such as DMF at the bottom.

Acetic acid of high purity is recovered to the top of the atmospheric distillation column, and it may have a purity of 95% or more, 97% or more, or 98% or more. At the bottom of the atmospheric distillation column, a mixture containing a carboxylic acid having a second azeotropic composition and an amide compound is obtained. The carboxylic acid and the amide compound having the second azeotropic composition are an azeotropic mixture under atmospheric pressure. Based on 100 parts by weight of the carboxylic acid and the amide compound having the second azeotropic composition, 20 to 30 parts by weight and 22 to 29 parts by weight of the carboxylic acid , or 24 to 28 parts by weight, in which case the carboxylic acid is acetic acid, and the component other than this may be composed of DMF.

However, in the case of batch distillation under atmospheric pressure, in the process of staying for about 10 hours in a heating flask at a high temperature, dimethylamine (Dimethylamine) generated by thermal decomposition of DMF is combined with acetic acid to produce DMAc (Dimethylacetamide) of about 10 % may be included in the residual liquid. Considering this decomposition, in the case of an atmospheric distillation column that recovers acetic acid to the top, it can be characterized by having a forced circulation reboiler suitable for heat-sensitive substances such as DMF. have.

All or a part of the mixture of the carboxylic acid and the amide compound having the second azeotropic composition obtained by the bottom of the atmospheric distillation column is recycled into the high vacuum distillation column. Therefore, it may be mixed with the feed input to the high vacuum distillation column in step S11 and put into the high vacuum distillation column. At this time, 1 to 100 parts by weight, 50 to 99.99 parts by weight, 80 to 99.9, or 90 to 99 parts by weight may be recycled based on 100 parts by weight of the mixture including the acetic acid and the amide compound having the second azeotropic composition. Except for the mixture comprising the acetic acid and the amide compound having a second azeotropic composition that is recycled, it may be discharged to the outside.

When the bottoms stream of the atmospheric distillation column is recycled to the vacuum column, as the composition difference between the vacuum azeotrope and the atmospheric azeotrope increases, the amount of recycling is reduced, and the operating cost is also reduced. When the differential pressure of the vacuum distillation column increases, the difference between the azeotropic composition of the bottom of the vacuum distillation column and the azeotropic composition of the bottom of the atmospheric distillation column decreases, and the amount of recycling increases.

The method for recovering the carboxylic acid and the amide compound according to the present invention may further include a step (S10) of pre-treatment before input to the high vacuum distillation column, which is a step of removing materials other than the carboxylic acid and the amide compound, which are the object of separation of the present invention, Before step S11, a waste solvent containing water, carboxylic acid, and an amide compound is put into the distillation column, and compounds other than carboxylic acid and amide compound, especially water, are separated and removed by the top of the distillation column, and carboxylic acid and amide are transferred to the bottom of the distillation column. It may include a step (S10) of obtaining a mixture containing the compound.

The spent solvent may further include a pyridine-based compound, and the pyridine-based compound may be separated by the top of the distillation column together with water in step S10. The pyridine-based compound may be 3-methylpyrinde (3MP).

Through the batch distillation experiment, it was confirmed that water and 3MP were sufficiently removable by the pretreatment step, and as a result of simulation using Aspen Plus, water and 3MP were removable by the top. In this case, in order to remove 3MP, a distillation column of 60 or more, 70 or more, or 80 or more stages is preferable as the actual number of stages.

In addition, as an embodiment of the present invention, in order to treat the waste solvent having the composition as shown in Table 2 below by combining the above-mentioned bars, one distillation column for removing water and 3MP, etc., and acetic acid-DMF after removing water and 3MP A process scheme as shown in FIG. 6 consisting of two distillation columns for pressure swing distillation for separation was derived.

	water	acetic acid (Acetic Acid)	3MP (3-methylpyridine)	DMF (Dimethylformamide)
boiling point, °C	100	118	143-144	153
composition ratio, %	10	15	2	73

As an embodiment of the present invention, each distillation column or step-by-step process of recovering acetic acid and DMF from the DMF waste liquid will be described with reference to the process scheme shown in FIG. 6 .

1. Step of removing water and 3MP to the top of the distillation column (S10)

Waste solvent containing water, acetic acid, DMF (Dimethylformamide), and 3MP is put into the distillation column, water and 3MP are removed through the top of the distillation column, and water and 3MP are removed from the bottom of the distillation column to obtain a mixture of acetic acid and DMF Step S10.

2. Recovering DMF to the top of the distillation column under high vacuum conditions (S11)

The acetic acid and DMF mixture obtained in step S10 is put into a distillation column under high vacuum conditions, DMF is recovered at the top of the distillation column, and a mixture of acetic acid and DMF having an azeotropic composition under high vacuum conditions is obtained at the bottom of the distillation column (S11).

3. Recovering acetic acid to the top of the distillation column under atmospheric conditions (S12)

The acetic acid and DMF mixture having an azeotropic composition under high vacuum conditions obtained in step S11 is put into a distillation column under atmospheric conditions, acetic acid is recovered at the top of the distillation column, and a mixture of acetic acid and DMF having an azeotropic composition under atmospheric conditions is obtained at the bottom of the distillation column (S12) .

4. Recirculating a portion of the distillation column bottoms stream under atmospheric conditions to the high vacuum distillation column (S13)

A part of the acetic acid and DMF mixture having an azeotropic composition under atmospheric conditions obtained in step S12, together with the acetic acid and DMF mixture obtained in step S10, is recycled to be introduced into the distillation column under high vacuum conditions in step S11 (S13).

On the other hand, in the method for recovering a carboxylic acid and an amide compound of the present invention, a mixture containing a carboxylic acid, an amide compound, and a quinoline-based compound is put into a high vacuum distillation column, the amide compound is recovered through the high vacuum distillation column top, and the high vacuum distillation column bottom is prepared 1 obtaining a mixture comprising a carboxylic acid having an azeotropic composition, an amide compound, and a quinoline-based compound (S21); The mixture containing the carboxylic acid, the amide compound, and the quinoline compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered at the top of the atmospheric distillation column, and the carboxylic acid and the amide having a second azeotropic composition at the bottom of the atmospheric distillation column obtaining a mixture comprising the compound, and a quinoline-based compound (S22); and a step (S23) of recirculating all or part of the mixture including the carboxylic acid having the second azeotropic composition, the amide compound, and the quinoline-based compound into the high vacuum distillation column (S23).

This is the same as the method for recovering the carboxylic acid and amide compound of the present invention described above, and overlapping description will be omitted.

In addition, all or part of the recirculated mixture including the carboxylic acid and the amide compound having the second azeotropic composition and the quinoline compound is separated from the acetic acid and the amide compound at the top of the column and the quinoline compound is separated at the bottom through a distillation column. After removing the quinoline-based compound, it may be introduced into the high vacuum distillation column. In this case, the carboxylic acid and the amide compound as well as the quinoline compound may be separated and recovered.

And, in the method for recovering the carboxylic acid and the amide compound of the present invention, before step S21, a waste solvent including water, a carboxylic acid, an amide compound, and a quinoline compound is added to the distillation column, and water is transferred to the top of the distillation column Separation and obtaining a mixture containing a carboxylic acid, an amide compound, and a quinoline-based compound to the bottom of the distillation column (S20); further comprising; it is preferable to first remove water prior to input to the high vacuum distillation column. Of course, when water is separated from the top, other components may be mixed with water and removed.

As described above, the carboxylic acid and the amide compound having the first azeotropic composition are azeotropic mixtures under high vacuum conditions, and 30 to 40 parts by weight of the carboxylic acid based on 100 parts by weight of the total of the carboxylic acid and the amide compound having the first azeotropic composition. , 32 to 38 parts by weight, or 33 to 37 parts by weight, in this case, the carboxylic acid is acetic acid and the component other than this may be composed of DMF.

In addition, the carboxylic acid and the amide compound having the second azeotropic composition are an azeotropic mixture under atmospheric pressure, and based on 100 parts by weight of the carboxylic acid and the amide compound having the second azeotropic composition, 20 to 30 parts by weight of the carboxylic acid, 22 to It may contain 29 parts by weight, or 24 to 28 parts by weight, wherein the carboxylic acid is acetic acid, and components other than this may be composed of DMF.

Referring to FIG. 7 which is an embodiment of the present invention, a waste solvent including water, a carboxylic acid, an amide compound, and a quinoline-based compound is added to the first distillation column 100, and water flows to the top of the first distillation column 100 to obtain a mixture containing a carboxylic acid, an amide compound, and a quinoline compound to the bottom of the first distillation column 100 (S20), and a carboxylic acid and an amide compound obtained to the bottom of the first distillation column 100, and a quinoline-based compound The mixture containing the compound is put into the high vacuum distillation column 200, the amide compound is recovered to the top of the high vacuum distillation column 200, and the carboxylic acid and the amide compound having a first azeotropic composition and the quinoline-based compound are collected at the bottom of the high vacuum distillation column 200 A mixture containing the mixture is obtained (S21). Then, the mixture containing the carboxylic acid and the amide compound having the first azeotropic composition obtained at the bottom of the high vacuum distillation column 200 is put into the atmospheric distillation column 300, the carboxylic acid is recovered to the top of the atmospheric distillation column 300, and the atmospheric distillation column (300) A mixture including a carboxylic acid having a second azeotropic composition, an amide compound, and a quinoline compound is obtained as the bottom of the column (S22). A part of the mixture containing the carboxylic acid and the amide compound having the second azeotropic composition, and the quinoline compound is put into the high vacuum distillation column 200 and recycled (S23), and the other part is sent to the second distillation column 400 to the bottom of the column. By separating the quinoline-based compound, the carboxylic acid and the amide compound recovered over the top may be combined with a stream fed into the high vacuum distillation column.

The quinoline-based compound may be quinoline, methylquinoline, or 3-methylquinoline.

The high vacuum distillation column may be a packing tower capable of minimizing the pressure difference between the top and the bottom in order to maintain the bottom pressure as low as possible.

The atmospheric distillation column may be a packing tower capable of minimizing the differential pressure between the top and the bottom in order to minimize the thermal decomposition of DMF at the bottom.

Although the process scheme derived from the present invention has been described step by step, the present invention is not limited to the above description. no.

[Example]

Preparation Example: Azeotropic composition analysis under vacuum conditions

As a preliminary experiment to confirm the azeotropic composition of acetic acid and DMF under vacuum pressure, 30 g of acetic acid and 70 g of DMF were put into a round flask for a rotary evaporator, and the distillate was added step by step at a bath temperature of 90°C and a vacuum pressure of 30 torr. While recovering, the content of acetic acid in the distillate and the residue was measured as shown in Table 3 below. Considering the measurement results in Table 3, it can be seen that the azeotropic composition at 30 torr is 36% or more of acetic acid, which is 10% or more higher than the azeotropic composition (26% of acetic acid) at atmospheric pressure.

	before distillation	1st stage distillation	two-stage distillation	3 stage distillation
recovered distillate		14g (acetic acid 17.4%)	22g (acetic acid 24.4%)	27g (33.2% acetic acid)
flask residue	100g (acetic acid 30.2%)	84g (31.2% acetic acid)	59g (acetic acid 34.4%)	30g (36.2% acetic acid)

Therefore, as a means for separating acetic acid and DMF azeotrope, it was determined that pressure swing distillation using the difference in azeotropic composition at atmospheric pressure and vacuum would be possible.

Example 1: Analysis of azeotropic composition according to the degree of vacuum (1)

A B/R 9600 Packed Column with a column inner diameter of 25 mm, the number of theoretical plates 45, and a 5-liter heating flask was used.

A batch distillation experiment was conducted under vacuum conditions (100 torr) by placing 2,000 cc of a mixture having an azeotropic composition at atmospheric pressure (acetic acid 26%, DMF 74%) into a heating flask, and acetic acid and DMF according to Cumulative Liquid Volume (CLV). The composition ratio of each sample is shown in FIG. 2 .

As shown in FIG. 2, high-purity DMF was obtained from the top, and a mixture having an azeotropic composition (34.0% acetic acid) of 100 torr was obtained as a residual liquid.

Example 2: Azeotropic composition analysis according to the degree of vacuum (2)

A B/R 9600 Packed Column with a column inner diameter of 25 mm, the number of theoretical plates 45, and a 5-liter heating flask was used.

2,000cc of a mixture having an azeotropic composition under atmospheric pressure (26% acetic acid, 74% DMF) was placed in a heating flask, and a batch distillation experiment was performed under vacuum conditions (50 torr). to obtain a mixture having an azeotropic composition (35.5% acetic acid) under 50 torr conditions.

Example 3: Azeotropic composition analysis according to the degree of vacuum (3)

A B/R 9600 Packed Column with a column inner diameter of 25 mm, the number of theoretical plates 45, and a 5-liter heating flask was used.

2,000cc of a mixture having an azeotropic composition (26% acetic acid, 74% DMF) under atmospheric pressure was placed in a heating flask and a batch distillation experiment was performed at 200 torr, high-purity DMF was obtained from the top of the column, and 200 torr condition as the residual solution A mixture having an azeotropic composition of (31% acetic acid) was obtained.

Example 4: Separation of acetic acid by atmospheric distillation

A B/R 9600 Packed Column with a column inner diameter of 25 mm, the number of theoretical plates 45, and a 5-liter heating flask was used.

2,000cc of a mixture having an azeotropic composition (acetic acid, 34%, DMF, 66%) of 100 torr obtained in Example 1 was put into a heating flask and a batch distillation experiment was performed under atmospheric conditions, and acetic acid according to Cumulative Liquid Volume (CLV) and DMF composition ratios for each sample are shown in FIG. 3 . As shown in FIG. 3 , 98.5% acetic acid was obtained from the top, and a mixture having an azeotropic composition (acetic acid 25.5%) under atmospheric conditions was obtained as a residual liquid.

4 shows the azeotrope composition according to pressure, and it was confirmed that the azeotropic composition of acetic acid and DMF in high vacuum (100 torr, 50 torr) conditions according to Examples 1 and 2 is significantly different from the azeotropic composition of atmospheric pressure, and the degree of vacuum It was confirmed that the ratio of acetic acid in the azeotrope composition increased with increasing . Therefore, it can be seen that the separation of a carboxylic acid such as acetic acid and an amide compound such as DMF can be effectively performed according to the waste solvent treatment method of the present invention.

At present, due to the economic and environmental problems of the caustic soda neutralization method, the recovery of DMF from the waste liquid including acetic acid and DMF is not sufficiently achieved. Based on the scheme derived from the present invention, DMF and It is expected that it will be possible to design a waste solvent treatment process that efficiently and economically recovers acetic acid.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments described above, and those skilled in the art can implement various modifications without departing from the gist of the present invention. Of course it is possible. Accordingly, the scope of the present invention should not be construed as limited to the above embodiments, and should be defined by the claims described below as well as the claims and equivalents.

Claims (13)

1. Putting a mixture containing a carboxylic acid and an amide compound into a high vacuum distillation column, recovering the amide compound to the top of the high vacuum distillation column, and obtaining a mixture containing a carboxylic acid having a first azeotropic composition and an amide compound to the bottom of the high vacuum distillation column (S11);

   The mixture containing the carboxylic acid and the amide compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered through the top of the atmospheric distillation column, and the mixture containing the carboxylic acid and the amide compound having the second azeotropic composition to the bottom of the atmospheric distillation column obtaining (S12); and

   A method of recovering a carboxylic acid and an amide compound, including a step (S13) of recycling all or a part of a mixture containing the carboxylic acid and the amide compound having the second azeotropic composition into the high vacuum distillation column.
2. The method according to claim 1,

   Before step S11,

   Putting a waste solvent including water, carboxylic acid, and an amide compound into a distillation column, separating water from the top of the distillation column, and obtaining a mixture containing a carboxylic acid and an amide compound with the bottom of the distillation column (S10); A method for recovering a carboxylic acid and an amide compound.
3. 3. The method according to claim 2,

   The waste solvent further includes a pyridine-based compound, and the pyridine-based compound is separated together with the water at the top of a distillation column.
4. The method according to claim 1,

   The method for recovering a carboxylic acid and an amide compound, characterized in that the carboxylic acid and the amide compound form an azeotropic mixture at a maximum temperature when mixed.
5. The method according to claim 1,

   The method for recovering a carboxylic acid and an amide compound, characterized in that the carboxylic acid is acetic acid and the amide compound is dimethylformamide.
6. The method according to claim 1,

   The high vacuum distillation column is a packing tower (Packing Tower), characterized in that, carboxylic acid and amide compound recovery method.
7. The method according to claim 1,

   The atmospheric distillation column is a packing tower (Packing Tower), characterized in that, carboxylic acid and amide compound recovery method.
8. A mixture containing a carboxylic acid, an amide compound, and a quinoline compound is put into a high vacuum distillation column, the amide compound is recovered at the top of the high vacuum distillation column, and a carboxylic acid and an amide compound having a first azeotropic composition, and a quinoline compound are obtained at the bottom of the high vacuum distillation column obtaining a mixture containing (S21);

   The mixture containing the carboxylic acid, the amide compound, and the quinoline compound having the first azeotropic composition is put into an atmospheric distillation column, the carboxylic acid is recovered at the top of the atmospheric distillation column, and the carboxylic acid and the amide having a second azeotropic composition at the bottom of the atmospheric distillation column obtaining a mixture comprising a compound, and a quinoline-based compound (S22); and

   A method of recovering a carboxylic acid and an amide compound, including a step (S23) of recycling all or a part of a mixture including the carboxylic acid and the amide compound having the second azeotropic composition and the quinoline-based compound into the high vacuum distillation column (S23); .
9. 9. The method of claim 8,

   The step (S24) of adding all or a part of the mixture including the carboxylic acid having the second azeotropic composition, the amide compound, and the quinoline compound to the distillation column to remove the quinoline compound and then to the high vacuum distillation column (S24); further comprising A method for recovering a carboxylic acid and an amide compound, characterized in that
10. 9. The method of claim 8,

    Before step S21,

    A waste solvent containing water, a carboxylic acid, an amide compound, and a quinoline compound is put into a distillation column, water is separated at the top of the distillation column, and a mixture containing a carboxylic acid, an amide compound, and a quinoline compound is obtained at the bottom of the distillation column. A method for recovering a carboxylic acid and an amide compound, comprising: obtaining (S20).
11. 9. The method of claim 8,

    The method for recovering a carboxylic acid and an amide compound, characterized in that the carboxylic acid is acetic acid and the amide compound is dimethylformamide.
12. 9. The method of claim 8,

    The high vacuum distillation column is a packing tower (Packing Tower), characterized in that, carboxylic acid and amide compound recovery method.
13. 9. The method of claim 8,

    The atmospheric distillation column is a packing tower (Packing Tower), characterized in that, carboxylic acid and amide compound recovery method.

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