Purification mode of perfluorinated solution

Abstract

The invention provides a purification mode of a perfluorinated solution, belongs to the technical field of fluorinated solution purification, and adopts a synergistic process technology of an adsorbent and step-by-step distillation based on significant difference of boiling points of components in a mixture. In the heating process, due to different boiling points, different components in the mixture are sequentially vaporized according to the sequence from low boiling points to high boiling points. When the temperature reaches the boiling point of a certain component, the component is quickly converted into a gas state, and other components with higher boiling points are still kept in a liquid state. Impurities in the target fluorinated liquid are vaporized preferentially by controlling the temperature and the heating rate, and preliminary separation of the impurities from the target fluorinated liquid is achieved. Meanwhile, the adsorbent can remove impurities in the fluorinated liquid through physical adsorption / chemical adsorption / electrostatic adsorption. Amorphous aluminum hydroxide adsorption and step-by-step distillation are innovatively combined, three major impurity removal principles of aluminum hydroxide are fully utilized, deep removal of impurities is realized, and the method is different from other single purification technologies.

Description

Technical Field

[0001] This application belongs to the technical field of purification of fluorinated liquids, and particularly relates to a purification method for perfluorinated solutions. Background Art

[0002] Many domestic manufacturers of electronic fluorinated liquids, such as Dongyue, Juhua, Lihua, Duofluoride, etc., generally use the method of preparing liquid hexafluoropropylene oligomers by the polymerization reaction of hexafluoropropylene gas through a catalyst to produce fluorocarbon solvents. In the actual production process, hexafluoropropylene gas is introduced into a reaction vessel equipped with a specific catalyst. Under certain temperature, pressure and reaction time conditions, hexafluoropropylene molecules undergo a polymerization reaction and gradually form liquid hexafluoropropylene oligomers. Although this method can achieve the large-scale production of fluorocarbon solvents, it inevitably introduces more impurities. During the reaction process, due to factors such as the purity of raw materials, the residue of the catalyst, and the fluctuation of reaction conditions, impurities such as water, alkali metal cyanides (such as potassium cyanate), and proton-inert solvents (such as ether) are mixed into the prepared fluorocarbon solvent. The presence of these impurities poses a potential hazard to the quality and performance of the subsequent anti-fingerprint agent. The main agent of the anti-fingerprint agent is usually perfluoropolyether siloxane. When it is directly stirred and mixed with the unpurified fluorinated liquid containing impurities, a series of chemical reactions will occur.

[0003] In terms of the shelf life, under normal circumstances, the effective use period of the anti-fingerprint agent should be more than 3 months to ensure the stability and usability of the product during production, storage and sales. The anti-fingerprint agent is composed of two parts: the main agent perfluoropolyether siloxane and the fluorinated liquid. The unpurified fluorinated liquid contains a large number of impurities, including water, alkali metal cyanides such as potassium cyanate, proton-inert solvents such as ether, etc. When perfluoropolyether siloxane is directly stirred and mixed with the unpurified fluorinated liquid and left to stand for a certain period of time, the presence of water will trigger a hydrolysis reaction, and impurities such as alkali metal cyanides and proton-inert solvents will also participate in and accelerate this reaction process. As time goes by, the hydrolysis reaction continues, and the molecular structure of perfluoropolyether siloxane is gradually destroyed, resulting in the anti-fingerprint agent losing its original anti-fingerprint effect. The shelf life is very short, perhaps only one month or even a few days. Once the hydrolysis reaction starts, it is an irreversible process, and the ineffective anti-fingerprint agent can only be scrapped, and the expensive main agent in the anti-fingerprint agent is equivalent to being wasted in vain, causing huge losses to the production enterprise. Currently, the method of using hexafluoropropylene gas through a catalyst polymerization reaction to prepare liquid hexafluoropropylene oligomers to produce fluorocarbon solvents contains more impurities, and traditional purification only relies on single distillation or adsorption, and cannot simultaneously remove chemical impurities (such as potassium cyanate) and physical mixing impurities (such as ether, water). Summary of the Invention

[0004] The present application provides a method for purifying a perfluorinated solution, aiming to solve, to a certain extent, the problem that traditional purification cannot synchronously remove chemical impurities and physical mixed impurities.

[0005] In a first aspect, the present application provides a method for purifying a perfluorinated solution, comprising the following steps:

[0006] S1. Adsorption: Take the fluorinated liquid to be purified, add an adsorbent, stir and adsorb to obtain the adsorbed fluorinated liquid;

[0007] S2. Preliminary purification: Heat the adsorbed fluorinated liquid to a first set temperature, evaporate to remove impurities, and evaporate to obtain a fluoride with a first boiling point and a preliminarily purified fluorinated liquid;

[0008] S3. Distillation purification: Heat the preliminarily purified fluoride obtained in S2 to a second set temperature while stirring, continuously heat, control the reflux ratio at a set value, and perform condensation under a vacuum state to collect the purified fluorinated liquid.

[0009] In some embodiments, the adsorbent in S1 is amorphous aluminum hydroxide, and the addition amount of the adsorbent is 0.4-0.8% of the total mass of the fluorinated liquid to be purified. The components of the unpurified fluorinated liquid are complex and contain impurities such as moisture, alkali metal cyanides (such as potassium cyanate), and proton-inert solvents (such as ether). The main function of using aluminum hydroxide is to adsorb free fluoride ions in the fluorinated liquid. The adsorption principle of aluminum hydroxide mainly includes the following aspects: Physical adsorption: Aluminum hydroxide has a porous structure and a large specific surface area, and can adsorb surrounding substances through physical action. Just like a sponge can adsorb water, the porous structure of aluminum hydroxide can accommodate and adsorb other molecules or ions. Chemical adsorption: Aluminum ions (Al 3+ ) in the solution can react with other ions to form stable compounds or complexes. For example, aluminum ions can combine with free fluoride ions (F - ) to form insoluble fluoroaluminum compounds, thereby realizing the adsorption and removal of fluoride ions. Electrostatic interaction: On the surface of aluminum hydroxide in the solution, there may be a certain charge. When there are ions with opposite charges in the solution, they will be attracted to each other through electrostatic attraction, thereby realizing adsorption. Using amorphous aluminum hydroxide (specific surface area ≥ 200 m 2 / g) as a multifunctional adsorbent, three types of impurities can be synchronously removed through physical adsorption (porous structure intercepts moisture / ether), chemical adsorption (Al 3+ reacts with F- to form AlF3 precipitate), and electrostatic interaction (neutralizes the negative charge of potassium cyanate).

[0010] In some embodiments, the first set temperature in S2 is 105°C - 108°C.

[0011] In some embodiments, the first-boiling-point fluoride in S2 includes hydrofluoroether, water, and hexafluoropropylene dimer.

[0012] In some embodiments, the boiling point of the first-boiling-point fluoride in S2 is 50 - 61 °C. The first-boiling-point fluoride is continuously heated while stirring until obvious stratification appears in the liquid. The upper clear liquid of the stratification in S3 includes water and ether, and the lower layer includes hydrofluoroether and hexafluoropropylene dimer.

[0013] In some embodiments, the second set temperature in S3 is 120 °C - 135 °C, and the set value of the reflux ratio is 3 - 5.

[0014] In some embodiments, the continuous heating in S3 is for 2 - 4 h, and the purified fluorination liquid in S3 is hexafluoropropylene trimer with a purity ≥ 99%.

[0015] In some embodiments, after the distillation and purification in S3, the remaining substances are continued to be distilled. The parameters are: the stirring speed is increased to 380 - 400 rpm, the distillation temperature is increased to 160 - 170 °C, until the remaining liquid in the reaction kettle is less than 2 L, and the reflux ratio is greater than 5 and then stopped. Solid-liquid separation is carried out to obtain aluminum hydroxide and the second-boiling-point fluorination liquid, and the boiling point of the second-boiling-point fluorination liquid > 200 °C.

[0016] In some embodiments, the stirring speed is 200 rpm - 300 rpm.

[0017] This solution divides the distillation into two stages - low-temperature stage (108 °C): preferentially separate low-boiling-point impurities (HFE, C6F 12 , water) to avoid side reactions between impurities and the main agent at high temperatures; high-temperature stage (135 °C + vacuum): precisely control the boiling point of C9F 18 (110 - 115 °C), and combine with a vacuum pump to reduce the system pressure and reduce the risk of thermal decomposition.

[0018] Compared with the prior art, the beneficial effects of this application are:

[0019] 1. The present invention provides a purification method for perfluorinated solutions, which is a synergistic process technology of adsorbent + fractional distillation based on the significant differences in the boiling points of the components in the mixture. During the heating process, due to the different boiling points of the different components in the mixture, they will vaporize in turn in the order of increasing boiling points. When the temperature reaches the boiling point of a certain component, this component rapidly transforms into a gaseous state, while other components with higher boiling points remain in a liquid state. By precisely controlling the temperature and heating rate, the impurities in the target fluorinated liquid are preferentially vaporized, achieving a preliminary separation from the target fluorinated liquid. At the same time, the adsorbent can remove the impurities in the fluorinated liquid through physical adsorption / chemical adsorption / electrostatic adsorption. Innovatively combining amorphous aluminum hydroxide adsorption with fractional distillation, and making full use of the three impurity removal principles of aluminum hydroxide, it realizes the deep removal of impurities, which is different from other single purification technologies.

[0020] 2. The present invention uses an accurate parameter control system to precisely control parameters such as temperature, stirring speed, and reflux ratio in segments. From the temperature setting in the heating-up stage, to the adjustment of the stirring speed in different stages, and the precise control of the reflux ratio, each parameter is set closely around the characteristics of the target fluorinated liquid and impurities, ensuring the purification effect and production efficiency. Detailed implementation manners

[0021] In order to make the technical problems to be solved, technical solutions and beneficial effects of this application clearer, the following further elaborates on this application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0022] In this application, the term "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0023] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression below refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a~b (that is, a and b), a~c, b~c, or a~b~c, where a, b, and c can be single or multiple respectively.

[0024] The terms "first" and "second" are used for descriptive purposes only to distinguish objects such as substances from each other, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0025] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise.

[0026] It should be understood that in various embodiments of the present application, the magnitude of the sequence numbers of the various processes does not mean the order of execution, and some or all of the steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0027] The weights of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the specific contents of the components, but also represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of the present application are scaled up or down in proportion, they are within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application may be mass units well known in the chemical field such as μg, mg, g, kg, etc.

[0028] Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0029] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present application can be obtained through the market or can be prepared by existing methods.

[0030] The technical solutions of the present application will be described below through specific examples and comparative examples.

[0031] To enable those skilled in the art to clearly understand the above implementation details and operations of the present application, and to significantly demonstrate the advanced performance of the embodiments of the present application, the above technical solutions will be illustrated by multiple examples below.

[0032] Example 1:

[0033] A purification method for a perfluorinated solution:

[0034] S1 Adsorption: Add aluminum hydroxide at 5% of the fluorination liquid as the adsorbent, stir and adsorb to obtain the fluorination liquid after adsorption.

[0035] During S2 preliminary purification, start the high-temperature circulator in the reaction tower, heat the fluorination liquid in the reaction kettle to about 105°C through oil bath heating, and evaporate the hydrofluoroether, hexafluoropropylene dimer, and water in the fluorination liquid. Under normal pressure, the boiling points of hydrofluoroether and hexafluoropropylene dimer are 50 - 61°C, and the boiling point of water is 100°C. Open the low-tower switch to let the distilled gas enter the low tower for condensation. To improve the condensation effect, turn on the low-temperature cooling circulator and use low-temperature liquid at 5°C for condensation, and collect it into the front kettle as the front kettle liquid. The liquid used in the low-temperature cooling circulator is a mixed liquid of water and alcohol with a ratio of 5:1. This is done to prevent the coolant from freezing due to overcooling and blocking the pipeline. Increasing the stirring speed helps the evaporation of the front kettle liquid. As the hydrofluoroether, ether, dimer, and water in the fluorination liquid evaporate, obvious stratification appears in the condensate in the spherical kettle. The density of water and ether is lower than that of hydrofluoroether and dimer, so they are in the upper layer, and the lower layer is the low-boiling fluorination liquid including hydrofluoroether and dimer, etc.

[0036] After the front kettle liquid is collected, close the low-tower switch, open the high-tower switch and raise the temperature to 135°C at the same time, start evaporation, and collect it into the rear kettle (the boiling point of hexafluoropropylene trimer is 110 - 115°C). Control the reflux ratio between 3 - 5. The higher the reflux ratio, the better the purification effect, but the lower the collection speed.

[0037] During S3 distillation purification, turn on the circulating water type vacuum pump to extract the distilled gas from the reaction kettle to the condensation pipeline, which can control the reflux ratio and improve the collection rate of the purified liquid. The vacuum pump is equipped with a pressure sensor to monitor the pressure in the reaction kettle in real time. When the pressure > 0.12 MPa, the system automatically cuts off the heating and triggers the pressure relief valve to automatically adjust the pumping rate to maintain a stable distillation efficiency; at the same time, it also reduces the pressure in the reaction kettle to prevent the occurrence of explosion of the kettle. Through continuous heating and distillation, the liquid is collected in the spherical rear kettle, and the rear kettle contains the final product hexafluoropropylene trimer required for this distillation purification.

[0038] Raise the distillation temperature to 160°C to increase the distillation speed of hexafluoropropylene trimer, and then discharge the high-boiling fluorination liquid remaining in the reaction kettle (the boiling point of hexafluoropropylene polymer > 200°C) and the adsorbent aluminum hydroxide in it through the bottom of the kettle, and separate and collect the aluminum hydroxide by filtering with a filter cloth.

[0039] In the steps of the embodiment, the vaporized steam enters the condensing device, and the gaseous components in the steam are recondensed into liquid under low temperature conditions. Due to the difference in physical properties between impurities and target fluorinated liquid during the condensation process, they will be collected in different containers respectively, thereby completing the complete separation of impurities and target fluorinated liquid. Impurities in fluorocarbon solvents are removed by adsorption and step-by-step distillation to obtain a pure electronic grade fluorinated liquid. The water content of this purified fluorinated liquid is below 3ppm, and the pH value is stable between 7-8. At the same time, the composition is relatively simple, and the boiling point of the solvent is stable, which is convenient for the adjustment and compounding of anti-fingerprint liquid, and also extends the shelf life to more than 6 months.

[0040] Comparative Example 1:

[0041] A method for purifying fluorinated liquid: a method for producing fluorocarbon solvents by preparing liquid hexafluoropropylene oligomers through a catalyst polymerization reaction of hexafluoropropylene gas. During the implementation process, it was found that the liquid contained a large amount of impurities, and traditional purification only relied on single distillation or adsorption, which could not simultaneously remove chemical impurities (such as potassium cyanate) and physical mixed impurities (such as ether and water).

[0042] Comparative Example 2:

[0043] A method for purifying fluorinated liquid: different from the embodiment in that activated carbon is used instead of aluminum hydroxide as an adsorbent.

[0044] During the implementation process, it was found that activated carbon can only physically adsorb water / ether, but cannot remove fluoride ions and potassium cyanate. After purification, the pH is still unstable (experimental data: pH = 6.2-7.5).

[0045] Comparative Example 3:

[0046] A method for purifying fluorinated liquid: Different from the embodiment, the whole process is vacuum distillation (not divided into stages).

[0047] During the implementation, it was found that: C6F 12 (boiling point 61°C) and C9F 18 (Boiling point 115℃) The boiling point difference is not big (61℃ vs.115℃), the azeotropic phenomenon leads to low separation efficiency and inability to separate low boiling point impurities and water (C9F 18 Purity ≤95%).

[0048] Test example:

[0049] The fluorinated liquids purified by the various schemes of Example 1 and the comparative example were tested respectively, and the results were shown in Table 1:

[0050] Table 1: Performance test results

[0051]

[0052]

[0053] The principles of impurity removal and shelf life extension in this solution are as follows:

[0054] Water: Free water is removed by low-temperature distillation (108 °C), and crystal water is adsorbed by aluminum hydroxide, making the total water content ≤ 3 ppm, blocking the chain reaction triggering of hydrolysis;

[0055] Potassium cyanate: The Al of aluminum hydroxide 3+ and CN - generate Al(CN)3 precipitate (Ksp = 1.3×10 -23 ), completely eliminating the interference of alkaline impurities on the pH value;

[0056] Solvents such as ether: Low-boiling impurities are precisely separated by fractional distillation (the boiling point of ether is 34.6 °C), preventing them from remaining in C9F 18 and triggering the oxidation of the main agent.

[0057] The industrial cost advantages of this solution are as follows:

[0058] Energy consumption reduction: Fractional distillation in stages (low temperature first and then high temperature) saves 30% energy compared to single high-temperature distillation;

[0059] Adsorbent reuse: The aluminum hydroxide separated by the filter cloth can be reused more than 5 times after high-temperature calcination (600 °C), and the raw material cost is reduced by 40%. In the above embodiments, the descriptions of each embodiment have their own focuses. For parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0060] The above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present application, and should all be included in the protection scope of the present application.

Claims

1. A purification method for a perfluorinated solution, characterized in that, It includes the following steps: S1, Adsorption: Take the fluorinated liquid to be purified, add an adsorbent, stir and adsorb to obtain the adsorbed fluorinated liquid; S2, Preliminary purification: Heat up the adsorbed fluorinated liquid to the first set temperature, evaporate and remove impurities, and evaporate to obtain the fluoride with the first boiling point and the preliminarily purified fluorinated liquid; S3, Distillation purification: Heat up the preliminarily purified fluoride obtained in S2 to the second set temperature while stirring, continuously heat, control the reflux ratio at the set value, and carry out condensation under a vacuum state to collect the purified fluorinated liquid.

2. The purification method of a perfluorinated solution according to claim 1, characterized in that, The adsorbent described in S1 is amorphous aluminum hydroxide, and the addition amount of the adsorbent is 0.4 - 0.8% of the total mass of the fluorinated liquid to be purified.

3. The purification method of a perfluorinated solution according to claim 1, characterized in that, The first set temperature described in S2 is 105°C - 108°C.

4. The purification method of a perfluorinated solution according to claim 1, characterized in that The fluoride with the first boiling point described in S2 includes hydrofluoroether, water, and hexafluoropropylene dimer.

5. The purification method of a perfluorinated solution according to claim 1, characterized in that The boiling point of the fluoride with the first boiling point described in S2 is 50 - 61°C. Continuously heat the fluoride with the first boiling point while stirring until obvious stratification occurs in the liquid. The supernatant of the stratification described in S3 includes water and ether, and the lower layer includes hydrofluoroether and hexafluoropropylene dimer.

6. The purification method of a perfluorinated solution according to claim 1, wherein, The second set temperature described in S3 is 120°C - 135°C, and the set value of the reflux ratio is 3 - 5.

7. The purification method of a perfluorinated solution according to claim 1, characterized in that, The continuous heating in S3 is 2 - 4h, and the purified fluorinated liquid described in S3 is hexafluoropropylene trimer with a purity ≥ 99%.

8. The purification method of a perfluorinated solution according to claim 1, wherein, After the distillation purification in S3, the remaining substance continues to be distilled. The parameters are: the stirring speed is increased to 380 - 400rpm, the distillation temperature is increased to 160 - 170°C, until the remaining liquid in the reaction kettle is less than 2L, and the reflux ratio is greater than 5 and then stop. Perform solid-liquid separation to obtain aluminum hydroxide and the fluoride with the second boiling point, and the boiling point of the fluoride with the second boiling point > 200°C.

9. The purification method of a perfluorinated solution according to claim 1, characterized in that, The stirring speed is 200rpm - 300rpm.

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