CN107176737A - The method that fluorine carbon solvent is extracted from perfluoro caprylic acid electrolysis by-products - Google Patents

Abstract

The invention relates to a method for extracting fluorocarbon solvents from perfluorooctanoic acid electrolysis by-products. The method uses electrolysis by-product fluorocarbon mixtures produced during the production process of perfluorooctanoic acid engineering production equipment as raw materials, and uses alkaline hydrolysis, water washing, drying, Distillation and filtration and other physical separation methods are used to separate and purify the by-products of electrolysis, extract fluorocarbon solvents, and realize the commercialization of by-products of PFOA electrolysis, which reduces the production cost of PFOA and improves the value of resource utilization. The method is applied in the production process and has the advantages of simple process, easy control and stable product quality.

Description

Method for extracting fluorocarbon solvent from perfluorooctanoic acid electrolysis by-product

technical field

The invention relates to the field of chemical technology, in particular to a method for extracting fluorocarbon solvents from perfluorooctanoic acid electrolysis by-products.

Background technique

High-quality fluorocarbon solvents have the characteristics of high stability and strong solubility. They are widely used in the cleaning and drying fields of precision electronics, instruments, equipment, high-density and large-capacity optical discs, and mobile phone communication tools. They have broad market prospects.

Fluorocarbon solvent is a by-product of electrolysis produced in the production process of perfluorooctanoic acid. Industrially, octanoyl chloride and hydrogen fluoride are used to electrolyze perfluorooctanoic acid to produce perfluorooctanoic acid, but the electrolysis process is often accompanied by some side reactions, and the by-product is mainly perfluoroepoxy ether , perfluoroheptane, etc., wherein the main reaction mechanism is as follows:

Main response:

(1) Electrolysis process

2HF→H ₂ +F ₂

(2) Fluorination reaction

C ₇ H ₁₅ COCl+15F ₂ →C ₇ F ₁₅ COF+14HF+HCl

(3) Neutralization reaction

C ₇ F ₁₅ COF+2NaOH→C ₇ F ₁₅ COONa+NaF+H ₂ O

NaOH+HF→NaF+ _H2O

(4) Acidification reaction

C ₇ F ₁₅ COONa+H ₂ SO ₄ →C ₇ F ₁₅ COOH+Na ₂ SO ₄

side effects:

(1) Electrolytic cyclization to generate perfluoro 2-n-butyltetrahydrofuran

(2) Electrolytic cyclization to generate perfluoro 2-n-propylpentane

(3) Octanoyl chloride is fluorinated and decarboxylated to produce perfluoroheptane in the presence of a small amount of water

C ₇ H ₁₅ COCl+H ₂ O+16F ₂ →C ₇ F ₁₆ +CO ₂ +HCl+16HF

After electrolysis, acidification, alkali washing, extraction and other methods are usually used to extract PFOA products from the electrolyte, and the remaining by-products are often disposed of as "three wastes" through incineration, and the value of resource utilization is not high. However, in recent years, with the continuous enhancement of environmental protection awareness and the prominent shortage of resources, people have begun to pay attention to and carry out the work of separating and refining the fluorocarbon mixture by-products of PFOA electrolysis. Carbon solvents are sold, or sold as products after simple washing and distillation. Due to the large amount of impurities, they cannot be used for cleaning precision electronics, instruments, equipment, high-density and large-capacity optical discs, and mobile phone communication tools. They can only be used for general cleaning. In the case of solvents and solvents, the field of use of fluorocarbon solvents is limited.

At present, there is no public report on the fine purification method of fluorocarbon solvent.

Contents of the invention

The purpose of the present invention is to provide a method for separation and purification to address the defects of the prior art that the by-products of perfluorooctanoic acid electrolysis are not high in utilization rate and incomplete purification. -2-n-butyltetrahydrofuran, perfluoro-2-n-propyl pentane, perfluoroheptane and a small amount of water and other fluorocarbon mixtures (by-products of perfluorooctanoic acid electrolysis) are separated and purified, and the obtained fluorocarbon Vegetable solvent has high purity, good quality and high utilization rate of resources.

One of technical solutions of the present invention is: the method for extracting fluorocarbon solvent from perfluorooctanoic acid electrolysis by-product, comprises the following steps:

(1) Alkaline hydrolysis: Add alkaline substances to the electrolytic by-product of perfluorooctanoic acid to carry out alkaline hydrolysis reaction;

(2) washing with water and drying: washing the alkaline hydrolysis reaction solution with water until the pH of the water layer is 7-8 to obtain a crude fluorocarbon solvent, and drying to remove the moisture in the crude fluorocarbon solvent;

(3) Distillation: Distill the dried crude fluorocarbon solvent, and take the fraction in the temperature range of 85-102°C.

In the present invention, the alkaline hydrolysis reaction is first performed on the electrolysis by-product of perfluorooctanoic acid, and the acidic substance in the electrolysis by-product can be removed by the alkali hydrolysis reaction, wherein the alkaline substance can be selected from an organic base or an inorganic base, and the inorganic base can be selected from sodium hydroxide One or more of calcium hydroxide and potassium hydroxide, the organic base can be selected from one or more of potassium tert-butoxide and sodium tert-butoxide, the present invention preferably adopts organic base, and further preferably adopts tert-butyl Potassium alkoxide as alkaline hydrolysis substance. The addition of the alkaline substance is 1-5% of the weight of the by-products of perfluorooctanoic acid electrolysis. Compared with the use of inorganic bases, the use of organic bases is more conducive to ensuring the full neutralization reaction when the by-products of perfluorooctanoic acid electrolysis are subjected to alkaline hydrolysis. to ensure the quality of the final product.

Preferably, the alkaline substance is formulated into an aqueous solution with a concentration of 5-40% and added to the electrolysis by-product of perfluorooctanoic acid, and the concentration is preferably 10-20%.

Further preferably, the conditions of the alkaline hydrolysis reaction are: temperature 20-50°C, reaction time 1-5h; more preferably: temperature 30-40°C, reaction time 3-4h.

The alkaline hydrolysis reaction is preferably carried out under stirring conditions.

After alkaline hydrolysis, the water-soluble substances produced in the alkaline hydrolysis process are removed by washing with water, and the impurities in the solvent are further removed. Water washing can be carried out with industrial water, deionized water or distilled water, preferably deionized water. The added amount of deionized water is preferably 1-2 times of the weight of the alkaline hydrolysis reaction solution. The number of washings is generally 3-8 times.

After washing with water, molecular sieve or activated carbon is used to remove the moisture in the crude fluorocarbon solvent, preferably molecular sieve is used, and the amount of molecular sieve is more preferably 10-20% of the weight of the crude fluorocarbon solvent. In addition, the use of molecular sieves or activated carbon to treat the solvent also has the effect of decolorization, which can further improve the quality of the solvent.

After washing with water, distillation means is used to further purify the solvent. The distillation can be carried out under normal pressure or under reduced pressure. The present invention preferably adopts normal pressure distillation, and normal pressure rectification can successfully realize the purification of the solvent, and Low energy consumption.

Preferably, the distillation reflux ratio is (1.5-2.5):1, more preferably 2:1.

In order to further improve the quality of the final product, the method of the present invention also includes a step of filtering the distilled product, and the filtering can further remove suspended solids and mechanical impurities in the solvent.

Preferably, the filtration uses one or more of alkaline clay, acid clay, diatomaceous earth and kaolin as the filter medium, more preferably diatomaceous earth.

Preferably, the amount of the filter medium is 5-20% by weight of the product, more preferably 5-10%.

Preferably, the filtration is pressure filtration, and the filtration pressure is 1-4kgf/cm ² , more preferably 1.5-2.5kgf/cm ² .

Using the above conditions can ideally remove suspended solids and mechanical impurities in the solvent, making the solvent clearer and of better quality.

The second technical solution of the present invention is: a fluorocarbon solvent prepared by any one of the above-mentioned methods.

Preferably, the fluorocarbon solvent includes perfluoro-2-n-butyltetrahydrofuran, perfluoro-2-n-propylpentane, and perfluoroheptane components.

Further preferably, the boiling range (101.3Kpa) of the fluorocarbon solvent is 85-102°C, the water content is ≤50PPm, and the pH value is 7-7.5.

On the basis of conforming to common knowledge in the field, the above-mentioned preferred conditions can be combined with each other to obtain preferred embodiments of the present invention.

After the above treatment, the prepared fluorocarbon solvent does not contain acidic substances, mechanical impurities and moisture. The product has high purity, high quality and good stability. It can be used in precision electronics, equipment, instruments, high-density and large-capacity optical discs, and collection and communication tools. Etc. cleaning and drying, has a broad market prospect.

detailed description

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. The reagents or substances involved in the examples are all commercially available, and the operations involved are routine operations in the art unless otherwise specified. The percentages involved in the present invention are mass percentages unless otherwise specified. The perfluorooctanoic acid electrolysis by-products involved in the examples are obtained by the following method: use octanoyl chloride and hydrogen fluoride as raw materials to electrolyze to produce perfluorooctanoic acid, and after the electrolysis, use acidification, alkali washing, and extraction methods to extract the perfluorooctanoic acid product from the electrolyte, and the remaining The liquid is the by-product of perfluorooctanoic acid electrolysis, which mainly contains perfluoro-2-n-butyltetrahydrofuran, perfluoro-2-n-propylpentyl ether, active ingredients of perfluoroheptane and other impurities.

Example 1

The method for extracting fluorocarbon solvent from perfluorooctanoic acid electrolysis by-product, comprises the steps:

(1) Alkaline hydrolysis: take 200 kg of perfluorooctanoic acid electrolysis by-products, add 20 kg of sodium hydroxide aqueous solution with a concentration of 10% to it, and react at 30 ° C for 4 hours under stirring;

(2) Washing: adding 1.5 times the weight of the reaction solution to the alkaline hydrolysis reaction solution with deionized water for washing, repeated washing for 5 times, the pH value of the water layer was measured to be 7.5, and the aqueous layer was discarded to obtain the crude fluorocarbon solvent;

(3) Drying: Add 20% molecular sieves by weight to the crude fluorocarbon solvent, dry for 12 hours under stirring, and separate to obtain a crude fluorocarbon mixture without water;

(4) Distillation: Add the obtained crude fluorocarbons to the rectification tower, carry out atmospheric distillation, control the reflux ratio to 2:1, and intercept and collect fractions in the temperature range of 80-100°C;

(5) Filtration: Add the collected cuts to the horizontal leaf filter, add diatomaceous earth with 5% weight of the cuts to start the precision filtration device, control the filtration pressure to be 2.5kgf/cm ² , implement the filtration operation, and collect the clear and transparent filtrate. Obtain 180kg fluorocarbon solvent finished product.

Example 2

The method for extracting fluorocarbon solvent from perfluorooctanoic acid electrolysis by-product, comprises the steps:

(1) Alkaline hydrolysis: take 200kg of perfluorooctanoic acid electrolysis by-products, add 40kg of potassium tert-butoxide aqueous solution with a concentration of 20% to it, and react at 30°C for 3h under stirring;

(2) Washing: add 1.5 times the weight of the reaction solution to the alkaline hydrolysis reaction solution with deionized water for washing, repeat the washing for 6 times, measure the pH value of the water layer to be 7.5, discard the water layer to obtain the crude fluorocarbon solvent;

(3) Drying: Add 20% molecular sieves by weight to the crude fluorocarbon solvent, dry for 24 hours under stirring, and separate to obtain a crude fluorocarbon mixture without water;

(4) Distillation: add the obtained crude fluorocarbons to the rectification tower, carry out atmospheric distillation, control the reflux ratio to 2:1, and intercept and collect fractions in the temperature range of 85-100°C;

(5) Filtration: Add the collected cuts into the horizontal blade filter, add 10% diatomaceous earth by weight of the cuts to start the precision filtration device, control the filtration pressure to be 2.5kgf/cm ² , implement the filtration operation, and collect the clear and transparent filtrate. Obtain 175kg fluorocarbon solvent finished product.

Example 3

The method for extracting fluorocarbon solvent from perfluorooctanoic acid electrolysis by-product, comprises the steps:

(1) Alkaline hydrolysis: take 200 kg of perfluorooctanoic acid electrolysis by-products, add 20 kg of potassium tert-butoxide aqueous solution with a concentration of 20%, and react at 30 ° C for 2 h under stirring;

(2) Washing: adding 1.5 times the weight of the reaction solution to the alkaline hydrolysis reaction solution with deionized water for washing, repeated washing for 5 times, the pH value of the water layer was measured to be 7, and the water layer was discarded to obtain the crude fluorocarbon solvent;

(3) Drying: add 10% molecular sieve by weight to the crude fluorocarbon solvent, dry for 24 hours under stirring, and separate to obtain a crude fluorocarbon mixture without water;

(4) Distillation: Add the obtained crude fluorocarbons to the rectification tower, carry out atmospheric distillation, control the reflux ratio to 2:1, and intercept and collect fractions in the temperature range of 88-100°C;

(5) Filtration: Add the collected cuts to the horizontal leaf filter, add diatomaceous earth with 5% weight of the cuts to start the precision filter device, control the filtration pressure to be 2kgf/cm ² , carry out the filtration operation, collect the clear and transparent filtrate, and obtain 185kg fluorocarbon solvent finished product.

Example 4

The operation of this embodiment is the same as that of embodiment 1, and its difference is only: in step (5), the filter medium is kaolin.

Example 5

The operation of this embodiment is the same as that of Example 1, and the only difference is that in step (3), 15% of its weight of gac is added to the crude fluorocarbon solvent to remove water, and the water removal time is 20 hours.

After testing, the technical index of the fluorocarbon solvent that embodiment 1 obtains is:

(1) Appearance: colorless transparent liquid, no mechanical impurities

(2) Boiling range (101.3KPa): 88～102℃

(3) Moisture content (PPm): 26

(4) pH value: 7.0

The technical index of the fluorocarbon solvent that embodiment 2 obtains is:

(1) Appearance: colorless transparent liquid, no mechanical impurities

(2) Boiling range (101.3KPa): 90～100℃

(3) Moisture content (PPm): 28

(4)PH value: 7.3

The technical index of the fluorocarbon solvent that embodiment 3 obtains is:

(1) Appearance: colorless transparent liquid, no mechanical impurities

(2) Boiling range (101.3KPa): 92～100℃

(3) Moisture content (PPm): 30

(4)PH value: 7.2

The technical index of the fluorocarbon solvent that embodiment 4 obtains is:

(1) Appearance: colorless transparent liquid, no mechanical impurities

(2) Boiling range (101.3KPa): 88～102℃

(3) Moisture content (PPm): 26

(4) pH value: 7.0

The technical index of the fluorocarbon solvent that embodiment 5 obtains is:

(1) Appearance: colorless transparent liquid, no mechanical impurities

(2) Boiling range (101.3KPa): 88～102℃

(3) Moisture content (PPm): 25

(4) pH value: 7.0

The fluorocarbon solvents prepared in Examples 1-5 are of good quality and can be used for cleaning and drying precision electronics, instruments, equipment, high-density and large-capacity optical disks, collection and communication tools, and the like.

Although, the present invention has been described in detail with general description, specific implementation and test above, but on the basis of the present invention, some modifications or improvements can be made to it, which will be obvious to those skilled in the art . Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. extracting the method for fluorine carbon solvent from perfluoro caprylic acid electrolysis by-products, its feature exists In comprising the following steps：

(1) alkaline hydrolysis：Alkaline matter is added into perfluoro caprylic acid electrolysis by-products, alkaline hydrolysis is carried out Reaction；

(2) wash and dry：Basic fluxing raction liquid is washed to water layer pH most 7-8, thick fluorine carbon is obtained Plain solvent, dries the moisture removed in the thick fluorocarbon solvent；

(3) distill：Dried thick fluorocarbon solvent is distilled, and takes 85-102 DEG C of temperature range Cut produce.

2. according to the method described in claim 1, it is characterised in that：The alkaline matter is One kind or several in sodium hydroxide, calcium hydroxide, potassium hydroxide, potassium tert-butoxide, sodium tert-butoxide Plant, preferably potassium tert-butoxide, it is further preferred that the addition of the alkaline matter is perfluor The 1-5% of sad electrolysis by-products weight.

3. method according to claim 1 or 2, it is characterised in that：By the alkalescence Material is configured to the concentration 5-40% aqueous solution and added in perfluoro caprylic acid electrolysis by-products, described dense Degree is preferably 10-20%.

4. the method according to claim any one of 1-3, it is characterised in that：The alkali Solving the condition reacted is：20-50 DEG C of temperature, reaction time 1-5h；Preferably：30-40 DEG C of temperature, Reaction time 3-4h.

5. the method according to claim any one of 1-4, it is characterised in that：Using point Moisture in son sieve or the activated carbon removing thick fluorocarbon solvent, preferably molecular sieve, further The consumption of preferred molecular sieve is the 10-20% of the thick fluorocarbon solvent weight.

6. the method according to claim any one of 1-5, it is characterised in that：It is described to steam Evaporate for air-distillation, preferably reflux ratio is (1.5-2.5)：1, more preferably 2:1.

7. the method according to claim any one of 1-6, it is characterised in that：Also include The step of being filtered to the product after distillation, the filtering using alkaline carclazyte, Emathlite, One or more as filter medium in diatomite, kaolin, preferably diatomite enters one The consumption for walking preferred filter media is the 5-20% of products weight.

8. the method according to claim any one of 1-7, it is characterised in that：The mistake Filter as pressure filtration, filter pressure is 1-4kgf/cm², preferably 1.5-2.5kgf/cm²。

9. any one of claim 1-8 methods described extracts obtained fluorine carbon solvent, it is special Levy and be：Including perfluor -2- normal-butyls tetrahydrofuran, the cyclic ethers of perfluor -2- n-propyls penta, perfluor Heptane component.

10. fluorine carbon solvent according to claim 9, it is characterised in that：The fluorine carbon 85-102 DEG C of the boiling range (101.3Kpa) of plain solvent, moisture≤50PPm, pH value 7-7.5.