CN117776999A - Purification method and application of N-methylpyrrolidone - Google Patents

Abstract

The invention provides a purification method and application of N-methyl pyrrolidone. The purification method comprises the following steps: after the first distillation of the solution to be purified, adding an extract, and performing a second distillation to obtain N-methylpyrrolidone, wherein the extract comprises N-heptane, diethyl ether and ethanone. The solution to be purified contains a compound with the boiling point similar to that of N-methylpyrrolidone, which is difficult to distill, N-heptane in the extract is used for inhibiting the boiling gasification of the N-methylpyrrolidone, and diethyl ether and ethyl ketone are used for changing the boiling point of impurities, so that the N-methylpyrrolidone is distilled out, and the high-efficiency separation and purification of the N-methylpyrrolidone are realized.

Description

Purification method and application of N-methylpyrrolidone

Technical Field

The invention belongs to the field of liquid phase extraction, and relates to a purification method and application of N-methylpyrrolidone.

Background

In many industrial and laboratory applications, the treatment of organic waste liquids and the recovery of resources are an important task. These effluents generally contain a plurality of organic components, some of which have different boiling points and chemical properties, making them difficult to separate and purify effectively.

CN111569457a discloses a method for recovering N-methylpyrrolidone. And (3) placing the solvent containing the polymer N-methyl pyrrolidone into a single-pass thin film evaporator for evaporation concentration, controlling the concentration ratio of the solvent to be 6-8, enabling the obtained gas-phase solvent to enter a condensing system for condensation through a gas-phase output port arranged at the top of the thin film evaporator, and finally performing dry distillation through a dry distillation device to complete the recovery of the N-methyl pyrrolidone.

CN116478077a discloses a method for removing low molecular polymer in cyclic solvent N-methyl pyrrolidone of acetylene plant. The low molecular polymer of the polycyclic aromatic hydrocarbon in the circulating solvent is removed by adopting a liquid phase extraction separation process, and a compound extractant is used, wherein the extractant is a mixture of long-chain alkane and hydroxyl-containing compound, and is separated by adopting an extraction tower, so that the method has the excellent performances of high selectivity and high removal rate.

However, when the concentration ratio is too high, there may occur problems of trace amounts of cina components (cina components refer to propylene glycol monomethyl ether and propylene glycol methyl ether acetate) which are difficult to distill out by the above-mentioned conventional rectification method, resulting in failure of the N-methylpyrrolidone to reach the acceptable purity standard, and for a mixture containing high boiling components such as a near boiling mixture of N-methylpyrrolidone, propylene glycol monomethyl ether, propylene glycol methyl ether acetate, etc., special methods are generally required to achieve efficient separation and purification.

Therefore, how to extract N-methyl pyrrolidone from high-boiling point multicomponent organic waste liquid efficiently, economically and sustainably is an important research direction in the field.

Disclosure of Invention

Aiming at the defects existing in the prior art, the invention aims to provide a high-efficiency, economical and sustainable purification method and application of N-methylpyrrolidone.

To achieve the purpose, the invention adopts the following technical scheme:

one of the purposes of the invention is to provide a purification method of N-methyl pyrrolidone, which comprises the following steps:

after the first distillation of the solution to be purified, adding an extract, and performing a second distillation to obtain N-methylpyrrolidone, wherein the extract comprises N-heptane, diethyl ether and ethanone.

The solution to be purified contains a compound with the boiling point similar to that of N-methyl pyrrolidone, the compound is difficult to distill, N-heptane in the extract is used for inhibiting boiling gasification of the N-methyl pyrrolidone, diethyl ether and ethyl ketone are used for changing the boiling point of impurities (the impurities refer to propylene glycol monomethyl ether and propylene glycol methyl ether acetate in the invention) so as to distill the impurities, the high-efficiency separation and purification of the N-methyl pyrrolidone are realized, and the added extract can be recovered in a cooling layering and distilling mode after the second distillation.

In a preferred embodiment of the present invention, the extract comprises 3 to 8% of n-heptane, 48 to 52% of diethyl ether and 40 to 49% of ethyl ketone by mass fraction, wherein the mass fraction of n-heptane may be 3%, 4%, 5%, 6%, 7% or 8%, the mass fraction of diethyl ether may be 48%, 49%, 50%, 51% or 52%, the mass fraction of ethyl ketone may be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48% or 49%, etc., but not limited to the listed values, and other non-listed values within the above-mentioned ranges are equally applicable.

In the invention, the gasification inhibition effect cannot be fully achieved due to the excessively low addition of the n-heptane, and the distillation efficiency is affected and the fraction disposal cost is increased due to the excessively high addition of the n-heptane; too low an amount of diethyl ether added has poor effect of changing the boiling point of propylene glycol monomethyl ether, and too high an amount of diethyl ether added affects distillation efficiency and results in higher cost of fraction disposal, which affects the effect of other substances in the extractant; too low an amount of ethyl ketone added has poor effect of changing the boiling point of propylene glycol methyl ether acetate, and too high an amount of ethyl ketone added affects distillation efficiency and results in higher cost of fraction disposal, which can affect the effect of other substances in the extractant.

As a preferable technical scheme of the invention, the solution to be purified comprises N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate.

The solution to be extracted contains a compound with the boiling point close to that of N-methyl pyrrolidone, wherein the boiling point of the N-methyl pyrrolidone is 202-204 ℃, the boiling point of propylene glycol monomethyl ether is 122-124 ℃, and the boiling point of propylene glycol methyl ether acetate is 145-148 ℃.

As a preferred embodiment of the present invention, the first distillation is carried out in a distillation column.

Preferably, in the first distillation, the bottom temperature of the distillation column is 140 to 150 ℃, wherein the bottom temperature may be 140 ℃, 141 ℃, 142 ℃, 143 ℃, 144 ℃, 145 ℃, 146 ℃, 147 ℃, 148 ℃, 149 ℃, 150 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable.

In the first distillation, N-methyl pyrrolidone is entrained and distilled out due to the fact that the temperature of the bottom of a distillation tower is too high, and propylene glycol methyl ether acetate is remained in the distillation tower due to the fact that the temperature of the bottom of the distillation tower is too low.

In the first distillation, the temperature of the distillation column top is preferably 115 to 125 ℃, wherein the temperature of the distillation column top may be 115 ℃, 116 ℃, 117 ℃, 118 ℃, 119 ℃, 120 ℃, 121 ℃, 122 ℃, 123 ℃, 124 ℃, 125 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable.

In the first distillation, N-methyl pyrrolidone is entrained and distilled out at the top temperature of a distillation tower, and the discharge of propylene glycol monomethyl ether and propylene glycol methyl ether acetate is not facilitated if the top temperature of the distillation tower is too low.

As a preferred technical scheme of the invention, the first distillation conditions are as follows: the extraction rate is more than or equal to 80 percent, the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified, wherein the extraction rate can be 80 percent, 81 percent, 82 percent, 83 percent, 84 percent, 85 percent, 86 percent, 87 percent, 88 percent, 89 percent or 90 percent, and the like, but the extraction rate is not limited to the recited values, and other non-recited values are applicable.

When the extraction rate is less than 80%, the extraction of propylene glycol methyl ether acetate and propylene glycol monomethyl ether can not entrain a large amount of N-methylpyrrolidone, thereby causing the loss of N-methylpyrrolidone. When the extraction rate is more than or equal to 80%, N-methyl pyrrolidone is distilled out in a large amount, at the moment, the first distillation is stopped, the extract is added, the boiling gasification of N-methyl pyrrolidone is inhibited, and the boiling points of compounds with similar boiling points to propylene glycol monomethyl ether and propylene glycol methyl ether acetate are changed, so that the compounds are separated and distilled out.

As a preferable technical scheme of the invention, the mass ratio of the extraction liquid to the residual impurities in the tail liquid after the first distillation is 1 (0.8-1.2), wherein the mass ratio can be 1:0.8, 1:0.9, 1:1.0, 1:1.1 or 1:1.2, and the like, but the invention is not limited to the listed values, and other non-listed values in the range of the values are equally applicable.

As a preferred technical scheme of the invention, the residual impurities comprise propylene glycol monomethyl ether and propylene glycol methyl ether acetate.

As a preferred embodiment of the present invention, the second distillation is carried out in a distillation column.

Preferably, in the second distillation, the bottom temperature of the distillation column is 115 to 125 ℃, wherein the bottom temperature may be 115 ℃, 116 ℃, 117 ℃, 118 ℃, 119 ℃, 120 ℃, 121 ℃, 122 ℃, 123 ℃, 124 ℃, 125 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable.

In the second distillation, N-methyl pyrrolidone is entrained and distilled out at the bottom of the distillation tower, and the discharge of propylene glycol monomethyl ether and propylene glycol methyl ether acetate is not facilitated if the bottom of the distillation tower is too low.

In the second distillation, the temperature at the top of the distillation column is preferably 100 to 110 ℃, wherein the temperature may be 100 ℃, 101 ℃, 102 ℃, 103 ℃, 104 ℃, 105 ℃, 106 ℃, 107 ℃, 108 ℃, 109 ℃, 110 ℃, or the like, but is not limited to the recited values, and other non-recited values within the range of the recited values are equally applicable.

In the second distillation, N-methyl pyrrolidone is carried and distilled out at the top of the distillation tower, and the too low top temperature of the distillation tower is unfavorable for the discharge of propylene glycol monomethyl ether and propylene glycol methyl ether acetate.

As a preferred embodiment of the present invention, the conditions for the second distillation are as follows: a second distillation no-fraction distillation;

preferably, the concentration of the N-methylpyrrolidone is not less than 99%, wherein the purity of the N-methylpyrrolidone may be 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 100%, etc., but not limited to the recited values, and other non-recited values within the range of values are equally applicable.

As a preferred technical scheme of the present invention, the purification method comprises:

carrying out first distillation on the solution to be purified at the bottom temperature of 140-150 ℃ and the top temperature of 115-125 ℃, adding the extraction liquid after the extraction rate is more than or equal to 80%, and carrying out second distillation on the solution at the bottom temperature of 115-125 ℃ and the top temperature of 100-110 ℃ to obtain N-methylpyrrolidone with the purity of more than or equal to 99%;

the solution to be purified comprises N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate;

the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified.

It is a second object of the present invention to provide an application of the method for purifying N-methylpyrrolidone according to one of the objects, which is applied to the field of liquid phase extraction.

The numerical ranges recited herein include not only the above-listed point values, but also any point values between the above-listed numerical ranges that are not listed, and are limited in space and for the sake of brevity, the present invention is not intended to be exhaustive of the specific point values that the stated ranges include.

Compared with the prior art, the invention has the beneficial effects that:

(1) The solution to be purified contains a compound with the boiling point similar to that of N-methylpyrrolidone, which is difficult to distill, N-heptane in the extract is used for inhibiting the boiling gasification of the N-methylpyrrolidone, and diethyl ether and ethyl ketone are used for changing the boiling point of the compound with the boiling point similar to that of the N-methylpyrrolidone, so that the compound is distilled, and the high-efficiency separation and purification of the N-methylpyrrolidone are realized;

(2) The purification of the N-methyl pyrrolidone meets the quality requirements of industrial and laboratory applications, and has wide application prospects in the field of waste liquid treatment;

(3) The invention obviously improves the purity of the N-methyl pyrrolidone to enable the N-methyl pyrrolidone to reach the required standard, and simultaneously recovers valuable components in the waste liquid, thereby reducing waste emission and resource waste.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments.

Example 1

This example provides a method for purifying N-methylpyrrolidone.

Solution to be purified: the mixed solution of N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate, wherein the ratio of the N-methyl pyrrolidone in the mixed solution is 11.7%, the rest is propylene glycol monomethyl ether and propylene glycol methyl ether acetate, and the weight of the solution to be purified is 300g.

Extract liquid: the mass of the extract is 100%, and the extract comprises 5% of n-heptane, 50% of diethyl ether and 45% of ethanone according to mass fraction.

And (3) carrying out first distillation on the solution to be purified at the bottom temperature of 145 ℃ and the top temperature of 120 ℃ until the extraction rate reaches 88%, wherein the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified, at the moment, adding 4.5g of extract, and then carrying out second distillation at the bottom temperature of 120 ℃ and the top temperature of 105 ℃, and carrying out second distillation until no fraction is distilled out, thus obtaining the N-methylpyrrolidone.

The changes in the content of N-methylpyrrolidone, the distillation temperature and the removal rate during the distillation process of this example were recorded as shown in Table 1.

TABLE 1

	Duty cycle of N-methylpyrrolidone	Bottom temperature of distillation tower	Rate of extraction
				First distillationFraction one	0.28％	145℃	38％
First distillation/fraction two	1.8％	145℃	60％
				First distillation/cut three	3.8％	145℃	81％
First distillation/cut four	10％	145℃	88％
				Second distillation/cut one	0.02％	120℃	89％
Second distillation/fraction two	/	120℃	91％

It is understood from Table 1 that when the extraction rate was 61%, the N-methylpyrrolidone content of the first fraction of the first distillation was 0.28%, the N-methylpyrrolidone content of the first and second fractions of the first distillation was gradually increased with increasing extraction rate until the N-methylpyrrolidone content of the fourth fraction of the first distillation was as high as 10%, the first distillation was stopped, the extract was added, and the second distillation was performed, as is known from the data of Table 1, the N-methylpyrrolidone content of the first fraction of the second distillation was reduced to 0.02%, the N-methylpyrrolidone concentration of the distillation tail was increased, and the boiling gasification of N-methylpyrrolidone was significantly suppressed by the addition of the extract.

Example 2

Solution to be purified: the mixed solution of N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate, wherein the ratio of the N-methyl pyrrolidone in the mixed solution is 11.7%, the rest is propylene glycol monomethyl ether and propylene glycol methyl ether acetate, and the weight of the solution to be purified is 300g.

Extract liquid: the mass of the extract is 100%, and the extract comprises 3% of n-heptane, 48% of diethyl ether and 49% of ethanone according to mass fraction.

And (3) carrying out first distillation on the solution to be purified at the bottom temperature of 140 ℃ and the top temperature of 115 ℃ until the extraction rate reaches 80%, wherein the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified, at the moment, adding 3.9g of extract, and then carrying out second distillation on the solution at the bottom temperature of 115 ℃ and the top temperature of 100 ℃, wherein the second distillation is carried out until no fraction is distilled out, so as to obtain the N-methylpyrrolidone.

Example 3

Solution to be purified: the mixed solution of N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate, wherein the ratio of the N-methyl pyrrolidone in the mixed solution is 11.7%, the rest is propylene glycol monomethyl ether and propylene glycol methyl ether acetate, and the weight of the solution to be purified is 300g.

Extract liquid: the mass of the extract is 100%, and the extract comprises 8% of n-heptane, 52% of diethyl ether and 40% of ethanone according to mass fraction.

And (3) carrying out first distillation on the solution to be purified at the bottom temperature of 150 ℃ and the top temperature of 125 ℃ until the extraction rate reaches 88%, wherein the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified, at the moment, adding 4.5g of extract, and then carrying out second distillation at the bottom temperature of 125 ℃ and the top temperature of 110 ℃, and carrying out second distillation until no fraction is distilled out, thereby obtaining the N-methylpyrrolidone.

Example 4

This example was conducted under the same conditions as in example 1 except that the bottom temperature of the first distillation was changed to 135 ℃.

Example 5

This example was conducted under the same conditions as in example 1 except that the bottom temperature of the second distillation was changed to 100 ℃.

Example 6

This example was conducted under the same conditions as in example 1 except that 5% n-heptane, 50% diethyl ether and 45% ethyl ketone were replaced with 20% n-heptane, 40% diethyl ether and 40% ethyl ketone.

Example 7

This example was conducted under the same conditions as in example 1 except that 5% n-heptane, 50% diethyl ether and 45% ethyl ketone were replaced with 0.5% n-heptane, 48.5% diethyl ether and 51% ethyl ketone.

Comparative example 1

The comparative example was conducted under the same conditions as in example 1 except that n-heptane was not added to the extract, and 50% diethyl ether and 50% ethyl ketone were used as the extract.

Comparative example 2

The comparative example was conducted under the same conditions as in example 1 except that diethyl ether was not added to the extract, and the extract was 5% n-heptane and 95% ethanone.

Comparative example 3

No acetone was added to the extract of this comparative example, and the extract was 5% n-heptane and 95% diethyl ether, under the same conditions as in example 1.

Comparative example 4

The comparative example was carried out without adding an extract.

The purity of N-methylpyrrolidone prepared in examples 1 to 7 and comparative examples 1 to 4 was measured, and the measurement results are shown in Table 2.

TABLE 2

As can be seen from Table 2, examples 1-3 and comparative example 4 show that N-heptane in the extract of the present invention is used to inhibit boiling gasification of N-methylpyrrolidone, diethyl ether and ethyl ketone are used to change boiling points of propylene glycol monomethyl ether and propylene glycol methyl ether acetate, so that the N-methylpyrrolidone is distilled out, and high-efficiency separation and purification of N-methylpyrrolidone are realized;

example 4 the bottom temperature of the first distillation was too low to allow distillation removal of propylene glycol monomethyl ether and propylene glycol methyl ether acetate;

example 5 the kettle bottom temperature of the second distillation was too low to reach the boiling point of the azeotrope after the extractant addition, resulting in poor distillation removal effect and extractant residue;

the N-heptane, diethyl ether and ethyl ketone contents in examples 6-7 were outside the preferred ranges, resulting in loss of N-methylpyrrolidone by boiling vaporization and entrained distillation by the azeotrope;

comparative example 1, without the addition of N-heptane, resulted in N-methylpyrrolidone boiling vaporization and loss by entraining distillation of the azeotrope;

the comparative examples 2-3 did not add diethyl ether or ethyl ketone, resulting in a propylene glycol monomethyl ether and propylene glycol methyl ether acetate azeotrope boiling point near N-methylpyrrolidone, which would be lost by substantial entrainment after reaching a certain removal rate.

While the foregoing is directed to embodiments of the present invention, other and further details of the invention may be had by the present invention, it should be understood that the foregoing description is merely illustrative of the present invention and that no limitations are intended to the scope of the invention, except insofar as modifications, equivalents, improvements or modifications are within the spirit and principles of the invention.

Claims (10)

1. A method for purifying N-methylpyrrolidone, the method comprising:

after the first distillation of the solution to be purified, adding an extract, and performing a second distillation to obtain N-methylpyrrolidone, wherein the extract comprises N-heptane, diethyl ether and ethanone.

2. The purification method according to claim 1, wherein the extract comprises 3 to 8% of n-heptane, 48 to 52% of diethyl ether and 40 to 49% of ethanone by mass fraction based on 100% of the mass of the extract.

3. The purification method according to claim 1, wherein the solution to be purified comprises N-methylpyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate.

4. A purification process according to any one of claims 1-3, wherein the first distillation is carried out in a distillation column;

preferably, in the first distillation, the bottom temperature of the distillation tower is 140-150 ℃;

preferably, in the first distillation, the temperature of the top of the distillation column is 115 to 125 ℃.

5. The purification process according to any one of claims 1 to 4, wherein the conditions for the first distillation are: the extraction rate is more than or equal to 80 percent, and the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified.

6. The purification method according to any one of claims 1 to 5, wherein the mass ratio of the extract to the residual impurities in the first distilled tail liquid is 1 (0.8 to 1.2);

preferably, the residual impurities include propylene glycol monomethyl ether and propylene glycol methyl ether acetate.

7. The purification process according to any one of claims 1 to 6, wherein the second distillation is performed in a distillation column;

preferably, in the second distillation, the bottom temperature of the distillation tower is 115-125 ℃;

preferably, in the second distillation, the temperature of the top of the distillation column is 100 to 110 ℃.

8. The purification process according to any one of claims 1 to 7, wherein the conditions for the second distillation are: a second distillation no-fraction distillation;

preferably, the concentration of the N-methylpyrrolidone is not less than 99%.

9. The purification method according to any one of claims 1 to 8, characterized in that the purification method comprises:

carrying out first distillation on the solution to be purified at the bottom temperature of 140-150 ℃ and the top temperature of 115-125 ℃, adding the extraction liquid after the extraction rate is more than or equal to 80%, and carrying out second distillation on the solution at the bottom temperature of 115-125 ℃ and the top temperature of 100-110 ℃ to obtain N-methylpyrrolidone with the purity of more than or equal to 99%;

the solution to be purified comprises N-methyl pyrrolidone, propylene glycol monomethyl ether and propylene glycol methyl ether acetate;

the extraction rate is the ratio of the weight of the fraction of the first distillation to the weight of the solution to be purified.

10. Use of a method for purifying N-methylpyrrolidone according to any one of claims 1 to 9, characterized in that the method is applied in the field of liquid phase extraction.