阅读说明：本技术 一种防止n-甲基吡咯烷酮变色劣化的方法及其制品 (Method for preventing discoloration and deterioration of N-methyl pyrrolidone and product thereof ) 是由 许林俊 王其合 吕远 陆建清 于 2020-07-22 设计创作，主要内容包括：本发明公开了一种防止N-甲基吡咯烷酮变色劣化的方法,通过对回收NMP原料进行预处理,并对工艺参数进行精确的控制,不仅可以防止回收料中原有的杂质引起产品变黄,还可以抑制精馏过程中产生新的不可测得的杂质。该方法虽然使用了较高浓度的碱性条件,但仍然保证了较高的收率和产品纯度,且产品在室温、高温条件下均不会出现变色,提高了客户使用满意度,在市场上具有广泛的推广价值。(The invention discloses a method for preventing N-methyl pyrrolidone from discoloring and deteriorating, which can prevent the yellowing of products caused by original impurities in recovered NMP materials and inhibit the generation of new and undetectable impurities in the rectification process by pretreating the recovered NMP materials and accurately controlling process parameters. The method ensures higher yield and product purity although the method uses the alkaline condition with higher concentration, and the product does not change color at room temperature and high temperature, thereby improving the satisfaction degree of customer use and having wide popularization value in the market.)

1. A method for preventing discoloration and deterioration of N-methylpyrrolidone, comprising the steps of:

a. pretreatment: adjusting the pH value of the NMP raw material to be treated to 10-11;

b. and (3) rectification: b, rectifying the material obtained in the step a by three towers; the third tower comprises a first tower kettle, a second tower kettle and a third tower kettle.

2. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 1, wherein step a is a pretreatment of: and adjusting the pH value of the NMP raw material to be treated to 10.1-10.9.

3. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 2, wherein step a is a pretreatment of: and adjusting the pH value of the NMP raw material to be treated to 10.2-10.8.

4. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 3, wherein said step a is a pretreatment of: and adjusting the pH value of the NMP raw material to be treated to 10.3-10.7.

5. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to any of claims 1 to 4, wherein in step a, the pH is adjusted using NaOH solution.

6. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 1, wherein the temperature of the first column bottom is 100 to 180 ℃ and the temperature of the top of the first column is 90 to 120 ℃.

7. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 1, wherein the temperature of the second column bottom is 95 to 160 ℃ and the temperature of the top of the second column is 90 to 150 ℃.

8. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 1, wherein the temperature of the column bottom of the third column bottom is 100 to 150 ℃ and the temperature of the column top is 95 to 145 ℃.

9. The method for preventing discoloration and deterioration of N-methylpyrrolidone, according to claim 1, wherein the second column bottom and the third column bottom are both negative pressure columns.

10. An article prepared using the method of any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of lithium battery solvent recovery, in particular to a method for preventing discoloration and deterioration of N-methyl pyrrolidone and a product thereof.

Background

N-methyl pyrrolidone, also known as N-methyl-2 pyrrolidone, is abbreviated as NMP for short, has CAS number of 872-50-4, is colorless transparent oily liquid in appearance, has slight amine smell, has the characteristics of low volatility, excellent thermal stability and excellent chemical stability, can dissolve most of organic and inorganic compounds, and is widely used in the fields of lithium batteries, electronic components and the like.

A large amount of NMP waste liquid can be generated in the production process of a lithium battery, in order to reduce cost, the NMP waste liquid can be recycled and purified and then reused, however, the problem that the product is yellowed after the recycled NMP is stored for a long time and the degree of color change gradually deepens along with the time extension, the use satisfaction of customers is seriously influenced, the yellowing substance of the product cannot be known through a common analysis and detection method, and the difficulty is increased for technical personnel in the field to solve the problem.

Disclosure of Invention

In order to solve the above problems, a first aspect of the present invention provides a method for preventing discoloration and deterioration of N-methylpyrrolidone, comprising the steps of:

a. pretreatment: adjusting the pH value of the NMP raw material to be treated to 10-11;

b. and (3) rectification: b, rectifying the material obtained in the step a by three towers; the third tower comprises a first tower kettle, a second tower kettle and a third tower kettle.

As a preferred technical solution, the step a is a pretreatment: and adjusting the pH value of the NMP raw material to be treated to 10.1-10.9.

As a preferred technical solution, the step a is a pretreatment: and adjusting the pH value of the NMP raw material to be treated to 10.2-10.8.

As a preferred technical solution, the step a is a pretreatment: and adjusting the pH value of the NMP raw material to be treated to 10.3-10.7.

As a preferable technical scheme, NaOH solution is used for adjusting the pH in the step a.

As a preferred technical scheme, the temperature of the tower kettle of the first tower kettle is 100-180 ℃, and the temperature of the tower top is 90-120 ℃.

As a preferred technical scheme, the temperature of the tower kettle of the second tower kettle is 95-160 ℃, and the temperature of the tower top is 90-150 ℃.

As a preferred technical scheme, the temperature of the tower kettle of the third tower kettle is 100-150 ℃, and the temperature of the tower top is 95-145 ℃.

As a preferred technical scheme, the second tower kettle and the third tower kettle are both negative pressure towers.

The second aspect of the present invention provides an article prepared using the above method.

Has the advantages that: the invention provides a method for preventing N-methyl pyrrolidone from discoloring and deteriorating, which can prevent the yellowing of products caused by original impurities in recovered NMP materials and inhibit the generation of new and undetectable impurities in the rectification process by pretreating the recovered NMP materials and accurately controlling process parameters. The method ensures higher yield and product purity although the method uses the alkaline condition with higher concentration, and the product does not change color at room temperature and high temperature, thereby improving the satisfaction degree of customer use and having wide popularization value in the market.

Drawings

To further illustrate the benefits of the method for preventing discoloration and deterioration of N-methylpyrrolidone and the product thereof, provided in the present invention, the accompanying drawings are provided, and it should be noted that the accompanying drawings provided in the present invention are only selected individual examples from all drawings and are not intended to limit the claims, and all other corresponding diagrams obtained through the drawings provided in the present application should be considered as within the protection scope of the present application.

FIG. 1 shows the results of room temperature stability tests of examples 1 and 10 of the present invention, wherein the left side is example 1 and the right side is example 10.

FIG. 2 is a photograph of the recovered NMP starting material after addition of base.

FIG. 3 is a photograph of recovered NMP starting material after addition of base.

FIG. 4 is a photograph of the recovered NMP starting material after addition of base and standing for a period of time.

FIG. 5 is a photograph of a sample of NMP of the present invention, the left sample being the final product of example 1, the middle sample being the overhead fraction of column one in example 1, and the right sample being the overhead fraction of column one in example 3.

FIG. 6 is a GC-MS spectrum of example 1 of the present invention.

FIG. 7 is a graph of the reaction paths that may occur during the rectification of a recovered NMP feed.

Detailed Description

The disclosure may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.

The term "prepared from …" as used herein is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or events may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification and claims, is intended to modify a quantity, such that the invention is not limited to the specific quantity, but includes portions that are literally received for modification without substantial change in the basic function to which the invention is related. Accordingly, the use of "about" to modify a numerical value means that the invention is not limited to the precise value. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. In the present description and claims, range limitations may be combined and/or interchanged, including all sub-ranges contained therein if not otherwise stated.

In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the stated number clearly indicates that the singular form is intended.

The present invention is illustrated by the following specific embodiments, but is not limited to the specific examples given below.

In order to solve the above problems, a first aspect of the present invention provides a method for preventing discoloration and deterioration of N-methylpyrrolidone, comprising the steps of:

a. pretreatment: adjusting the pH value of the NMP raw material to be treated to 10-11;

b. and (3) rectification: b, rectifying the material obtained in the step a by three towers; the third tower comprises a first tower kettle, a second tower kettle and a third tower kettle.

In some embodiments, the step a is a pretreatment: adjusting the pH value of the NMP raw material to be treated to 10.1-10.9; preferably, the step a is a pretreatment: adjusting the pH value of the NMP raw material to be treated to 10.2-10.8; further preferably, the step a is a pretreatment: adjusting the pH value of the NMP raw material to be treated to 10.3-10.7; further, the step a is pretreatment: adjusting the pH value of the NMP raw material to be treated to 10.4-10.6; most preferably, the step a is a pretreatment: the pH of the NMP feedstock to be treated was adjusted to 10.5.

The method of measuring pH in the present application may be any one known to those skilled in the art, for example, measurement using a pH meter.

The method of adjusting the pH in the present application may be any known to those skilled in the art, and for example, the pH can be adjusted by using a pH adjuster such as sodium hydroxide solution, potassium hydroxide solution, ammonia water, hydrochloric acid, acetic acid, citric acid, or the like.

In some preferred embodiments, the pH is adjusted in step a using NaOH solution.

The NaOH solution can be formulated in a manner well known to those skilled in the art, for example by dissolving solid sodium hydroxide in water. The concentration of the NaOH solution is not particularly limited in this application, and may be formulated as required, and typically a 30 wt% NaOH solution may be selected.

The inventor finds in production practice that the high-purity product extracted by recovering the NMP is easy to discolor and yellow during storage, the yellowing degree of the product is deeper as time goes on, or the NMP is discolored when being heated during use, but the discoloration caused by the substance cannot be known through gas chromatography. The inventor unexpectedly found that the raw material of NMP after being recovered and added with alkali turns pink or purple red (see fig. 2 and fig. 3, the color of the solution is different depending on the pH), and the raw material gradually turns yellow (see fig. 4) after the storage time is prolonged, so the NMP is supposed to turn yellow due to the polymerization of the hydrolyzed product of NMP, and the reaction route thereof is exemplified by several kinds of NMP, but not limited to the exemplified reaction route, the hydrolyzed product of NMP is more various and contains various active groups, such as hydroxyl, carboxyl, amino, acyl and the like, which are subjected to a series of complex reactions such as cyclization, polycondensation and the like during the high-temperature rectification process, and the discoloration phenomenon is difficult to be effectively solved. Generally, increasing the pH of an NMP raw material accelerates the hydrolysis of NMP, which brings negative effects and results in a decrease in yield and purity, however, the inventors found in continuous research and a great deal of practice that the pH of the recovered NMP raw material is very strictly controlled, which can significantly improve the yellowing phenomenon of the product, because the recovered NMP contains a certain hydrolysate, and under the condition of alkaline catalysis, the hydrolysate becomes a heavy component after being polymerized, and can be separated from purified NMP, so that the hydrolysate and NMP are prevented from being azeotroped to cause a great amount of hydrolysate to be mixed into the product, if the pH value is too high, the NMP is hydrolyzed in a great amount, the yield and purity are greatly decreased, and the discoloration phenomenon cannot be solved, but becomes more serious, and the raw material may be salted out and layered, which increases the process difficulty; if the pH value is too low, the hydrolysate generated in the rectification process cannot be effectively separated from NMP, and the yellowing problem still exists.

In some preferred embodiments, the temperature of the first tower kettle is 100-180 ℃, and the temperature of the top of the first tower kettle is 90-120 ℃; further preferably, the temperature of the first tower kettle is 105-178 ℃, and the temperature of the top of the first tower kettle is 92-118 ℃; furthermore, the temperature of the first tower kettle is 115-175 ℃, and the temperature of the top of the first tower kettle is 95-100 ℃.

In some preferred embodiments, the temperature of the second tower kettle is 95-160 ℃, and the temperature of the top of the second tower kettle is 90-150 ℃; further preferably, the temperature of the tower kettle of the second tower kettle is 100-155 ℃, and the temperature of the tower top is 95-140 ℃; furthermore, the temperature of the second tower kettle is 105-145 ℃, and the temperature of the top of the second tower kettle is 100-130 ℃.

In some preferred embodiments, the temperature of the tower kettle of the third tower kettle is 100-150 ℃, and the temperature of the tower top is 95-145 ℃; further preferably, the temperature of the tower kettle of the third tower kettle is 105-145 ℃, and the temperature of the tower top is 100-140 ℃; furthermore, the temperature of the third tower kettle is 110-135 ℃, and the temperature of the top of the third tower kettle is 105-135 ℃.

The inventor researches and discovers that NMP has polarity and can form hydrogen bonds with water molecules, so that the hydrolysis degree under normal temperature and neutral conditions is not high, however, due to the addition of alkali, the hydrolysis activation energy of NMP is reduced, and the hydrogen bonds between NMP and water molecules are broken by high temperature, so that the hydrolysis rate of NMP is increased, the hydrolysis products in the system are increased, and the further polymerization reaction of the hydrolysis products is simultaneously carried out under high temperature and alkaline conditions, so that the reaction path is more difficult to accurately control. The inventor finally determines an optimal temperature range in repeated experiments, solves the problem of product discoloration on the premise of ensuring the yield and purity, greatly reduces the yield and purity of the product when the process temperature is higher than the optimal range, increases the impurities at the bottom of the kettle, increases the treatment cost of later-stage wastes, and otherwise, insufficiently separates NMP from liquid impurities and has unqualified product purity when the process temperature is lower than the optimal range. In addition, the purification of NMP is carried out step by a three-stage rectification mode, and the method has positive effects on the improvement of yield and purity.

In some preferred embodiments, the first column is an atmospheric or negative pressure column.

In some preferred embodiments, when the first tower kettle is a negative pressure tower, the pressure of the first tower kettle is-70 to-101 kPa, and the pressure of the tower top is-75 to-101 kPa; further preferably, the pressure of the tower bottom of the first tower bottom is-75 to-98 kPa, and the pressure of the tower top is-80 to-99 kPa; furthermore, the pressure of the first tower kettle is-80 to-95 kPa, and the pressure of the top of the first tower kettle is-85 to-95 kPa.

In some preferred embodiments, the second tower kettle and the third tower kettle are both negative pressure towers.

In some preferred embodiments, the pressure in the second tower kettle is-70 to-101 kPa, and the pressure in the tower top is-75 to-101 kPa; further preferably, the pressure of the tower bottom of the second tower bottom is-75 to-98 kPa, and the pressure of the tower top is-80 to-99 kPa; furthermore, the pressure of the second tower kettle is-80 to-95 kPa, and the pressure of the top of the second tower kettle is-85 to-95 kPa.

In some preferred embodiments, the pressure of the tower bottom of the tower III is-70 to-101 kPa, and the pressure of the tower top is-75 to-101 kPa; further preferably, the pressure of the tower kettle of the third tower kettle is-75 to-98 kPa, and the pressure of the tower top is-80 to-99 kPa; furthermore, the pressure of the third tower kettle is-80 to-95 kPa, and the pressure of the top of the third tower kettle is-85 to-95 kPa.

The negative pressure tower in the application refers to a rectifying tower with the pressure in the tower lower than the atmospheric pressure; in the present application, the column bottom pressure and the column top pressure are relative pressures, that is, pressures expressed based on atmospheric pressure 1atm, where 1atm is 101.325 kPa.

In chemical production, the pressure of a rectifying tower determines the treatment capacity of the tower, and under normal conditions, the pressure is increased, so that the treatment capacity of the rectifying tower is increased, and the production efficiency is higher.

In some embodiments, the method further comprises step c: and (6) packaging and storing.

In this application packing and storage go on according to normal standard, keep out of the sun and preserve, store in shady and cool ventilation drying department.

The second aspect of the present invention provides an article prepared using the above method.