CN111170888A - Method for purifying heptafluoroisobutyronitrile - Google Patents
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Abstract
The invention discloses a method for purifying heptafluoroisobutyronitrile, which is used for obtaining a heptafluoroisobutyronitrile product after adsorbing, rectifying and deeply adsorbing crude heptafluoroisobutyronitrile gas and comprises the following steps: (1) introducing the crude gas of heptafluoroisobutyronitrile into a first-stage adsorption column, and removing water and part of organic impurities; (2) the adsorbed heptafluoroisobutyronitrile enters a light component removing rectifying tower to be continuously rectified to remove light component impurities, and the gas after light component removal enters a heavy component removing rectifying tower to remove heavy component impurities; (3) and (3) the removed heptafluoroisobutyronitrile gas passes through a secondary adsorption column, the residual isomer heptafluoron-butyronitrile is removed by deep adsorption, and a heptafluoroisobutyronitrile product is collected. The method has simple process, continuous operation and easy realization of industrialization.
Description
Technical Field
The invention relates to a method for purifying heptafluoroisobutyronitrile.
Background
The heptafluoroisobutyronitrile is a novel environment-friendly insulating gas material, has the characteristics of low boiling point, high volatility, excellent electrical insulating property, good environment-friendly performance and the like, and can be used as a dielectric composition of an insulator of electrical equipment. The greenhouse effect index (GWP) of heptafluoroisobutyronitrile is only 2210 and is far lower than that of sulfur hexafluoride (GWP is 23500), so that the heptafluoroisobutyronitrile can be used for replacing the traditional sulfur hexafluoride insulating gas, and the problem of the atmospheric greenhouse effect is greatly reduced. Heptafluoroisobutyronitrile has received much attention from the global electrical industry and is beginning to find application.
US2015/0083979a1 discloses a preparation process by an electrolytic fluorination method: the method comprises the steps of taking isobutyric anhydride as a starting material, carrying out electrolytic fluorination on isobutyric anhydride and hydrogen fluoride in an electrochemical reactor to obtain heptafluoro isobutyryl fluoride, carrying out rectification, separation and purification on the heptafluoro isobutyryl fluoride, carrying out esterification on the heptafluoro isobutyric acid methyl ester and methanol to obtain heptafluoro isobutyronitrile, and then preparing heptafluoro isobutyronitrile. The method has the key steps that a certain amount of isomerization by-product heptafluoro-n-butyryl fluoride is inevitably generated in the preparation of heptafluoro isobutyryl fluoride through electrolytic fluorination, so that impurities such as isomer heptafluoro-n-butyronitrile, heptafluoro-acetonitrile, heptafluoro-propionitrile and the like are introduced into heptafluoro isobutyronitrile. Patent documents CN 108395382A, CN 108424375A, CN 108863847 a and the like report a process for preparing heptafluoroisobutyronitrile by acylation and addition using hexafluoropropylene as a raw material, and a small amount of impurities such as hexafluoropropylene and the isomer heptafluoron-butyronitrile are introduced in the preparation process.
The heptafluoro-n-butyronitrile and heptafluoro-isobutyronitrile have similar boiling points and properties, the separation difficulty is high, the 50% lethal concentration (LC-50) absorbed in 4 hours is 2.5 times of that of the heptafluoro-isobutyronitrile, the toxicity is high, and in addition, the existence of impurities such as nitrogen, oxygen, carbon dioxide, hexafluoropropylene, moisture and the like introduced in the preparation process of the heptafluoro-isobutyronitrile has important influence on electrical insulation and safe use. The method for removing the above impurities in heptafluoroisobutyronitrile has not been reported.
Disclosure of Invention
The invention aims to provide a method for purifying heptafluoroisobutyronitrile.
In order to achieve the purpose, the technical scheme of the invention is as follows: a method for purifying heptafluoroisobutyronitrile is to obtain a heptafluoroisobutyronitrile product by adsorbing, rectifying and deeply adsorbing crude heptafluoroisobutyronitrile gas, and comprises the following steps:
(1) introducing the crude gas of the heptafluoroisobutyronitrile into a first-stage adsorption column to remove water and part of organic impurities.
(2) And (3) the adsorbed heptafluoroisobutyronitrile enters a light component removing rectifying tower to be continuously rectified to remove light component impurities, and the gas after light component removal enters a heavy component removing rectifying tower to remove heavy component impurities. Impurities such as nitrogen, oxygen, carbon dioxide, hexafluoropropylene, C1-C3 subfluoride and the like are removed from the top of the light rectifying tower; the heavy component removed by the heavy component removing rectifying tower is most of heavy components such as heptafluoro-n-butyronitrile and methyl trifluoroacetate.
(3) And (3) the removed heptafluoroisobutyronitrile gas passes through a secondary adsorption column, the residual isomer heptafluoron-butyronitrile is removed by deep adsorption, and a heptafluoroisobutyronitrile product is collected.
The volume content of the heptafluoroisobutyronitrile in the crude heptafluoroisobutyronitrile gas is generally not less than 80 percent, preferably more than 90 percent, wherein the impurities mainly comprise: (a) o is2、N2、CO2Light components such as perfluoroacetonitrile, perfluoropropionitrile, hexafluoropropylene and the like; (b) heptafluoro-n-butyronitrile, methyl trifluoroacetate and other heavy components; (c) h2O。
The adsorbent in the first-stage adsorption column in the step (1) is preferably silica gel, activated alumina and an A-type molecular sieve, and is preferably a 3A-type molecular sieve.
The adsorption process conditions in the step (1) are generally as follows: the temperature is 40-100 ℃, preferably 40-70 ℃, and the crude gas can be ensured to enter the rectifying tower in a continuous airflow mode; the pressure is 0.3-0.6 MPa, preferably 0.4 MPa; the gas flow is 0.1-10 kg/h, and the airspeed is 10-1000 h-1Preferably, the gas flow is 0.1-2 kg/h, and the space velocity is 10-500 h-1。
In the step (2), the light component removal rectifying tower has the tower pressure of 0.15-0.3 MPa, the tower kettle temperature of 20-30 ℃ and the tower top temperature of 15-25 ℃. And (4) introducing the light components at the top of the tower into a tail gas catcher, and transferring the liquid phase at the bottom of the tower to a heavy component removal rectifying tower when the content of the light components in the tower kettle is less than 0.2%.
In the heavy component removing rectifying tower in the step (2), the tower pressure is 0.05-0.15 MPa, the temperature of a tower kettle is 10-20 ℃, the temperature of a tower top is 5-15 ℃, high boiling point impurities such as heptafluoro-n-butyronitrile, methyl trifluoroacetate and the like are rich and discharged from the kettle bottom, the content of heavy components at the tower top is analyzed, and when the content is less than 0.2%, the gas phase of the components at the tower top enters a secondary adsorption column.
And (4) in the step (3), the secondary adsorption column is used, wherein the adsorbent is active carbon, a molecular sieve and the like. Coconut shell activated carbon and F03 molecular sieve are preferred. The adsorption temperature is 20-30 ℃, the pressure is 0-0.15 MPa, and the gas flow is 10-1000g/h, and the airspeed of 10-300 h-1And when the content of the isomer heptafluoro-n-butyronitrile in the outlet of the secondary adsorption column is monitored to be less than 0.1 percent, collecting a finished product. The temperature of the heptafluoro-n-butyronitrile low-temperature storage tank is generally-10 to-30 ℃.
The gas components in each process of the method can be monitored and analyzed on line by a gas chromatograph. The method provided by the invention can prepare a heptafluoroisobutyronitrile product with the purity of more than 99.5 percent (area percentage content), the water content is lower than 10ppmv, and the fluorine n-butyronitrile content of the isomer is not higher than 0.05 percent (area percentage content).
The method provided by the invention has the advantages of simple process, continuous operation and easy realization of industrialization.
Drawings
FIG. 1 is a process flow diagram for purifying heptafluoroisobutyronitrile.
Wherein: 1. first grade adsorption column, 2. light-removing rectifying tower, 3. heavy-removing rectifying tower, 4. second grade adsorption column, 5. low-temp. storage tank, 6. tail gas collector
Detailed Description
The present invention will be described in further detail with reference to examples, but the present invention is not limited to the following examples. The following percentage contents are all area percentage contents.
The crude gas of heptafluoroisobutyric acid is analyzed by gas chromatography, wherein the purity of heptafluoroisobutyronitrile is 92.2%, the total amount of oxygen and nitrogen is 2.7%, the content of carbon dioxide is 0.1%, the content of perfluoroacetonitrile is 0.3%, the content of perfluoropropionitrile is 0.6%, the content of hexafluoropropylene is 1.3%, the content of perfluoro-n-butyronitrile is 2.5%, and the content of methyl trifluoroacetate is 0.3%.
Example 1
Heating crude gas of heptafluoro isobutyl to 40 ℃, the pressure is 0.5MPa, the gas flow is 1kg/h, and the space velocity is 300h-1And the gas enters a first-stage adsorption column (active alumina is used as a filler), the adsorbed heptafluoroisobutyronitrile gas enters a light component removal rectifying tower, the pressure in the light component removal rectifying tower is 0.21MPa, the temperature of a tower kettle is 27.5 ℃, and the temperature of a tower top is 22.5 ℃. And (3) sampling and analyzing the content of low-boiling-point impurities in the tower kettle, wherein the total content of oxygen and nitrogen is 0.1%, the content of hexafluoropropylene is 0.04%, and other low-boiling-point impurities are not detected. The product extracted from the tower bottom enters a heavy component removing rectifying towerThe pressure in the heavy component removing rectifying tower is 0.12MPa, the temperature of the tower bottom is 19.0 ℃, and the temperature of the tower top is 13.5 ℃. And (3) sampling and analyzing the content of high-boiling-point impurities at the top of the tower, wherein the content of the heptafluoro n-butyronitrile is 0.15%, and other high-boiling-point impurities are not detected, extracting a gas phase at the top of the tower into a secondary adsorption column (an adsorbent is coconut shell activated carbon), detecting the content of the heptafluoro n-butyronitrile at the outlet of the sampling and analyzing adsorption column, and cooling and storing the product extracted from the outlet of the adsorption column into a low-temperature storage tank at the temperature of-10 ℃ to finish product filling. The product analysis results are shown in Table 1.
Example 2
In the same manner as in example 1, the crude gas pressure of the crude heptafluoroisobutyl gas was 0.3MPa, the gas flow rate was 2kg/h, and the space velocity was 500h-1And the gas enters a first-stage adsorption column (silica gel is used as a filler), the adsorbed heptafluoroisobutyronitrile gas enters a light component removing rectifying tower, the pressure in the light component removing rectifying tower is 0.17MPa, the temperature of a tower kettle is 25.5 ℃, and the temperature of a tower top is 21.0 ℃. The low boiling point impurity content in the bottom of the tower is sampled and analyzed, wherein the total content of oxygen and nitrogen is 0.16 percent, the content of hexafluoropropylene is 0.22 percent, and CO is2The content is 0.03 percent, and other low boiling point impurities are not detected. The product extracted from the tower bottom enters a weight removal tower, the pressure in the weight removal rectifying tower is 0.10MPa, the temperature of the tower bottom is 17.0 ℃, and the temperature of the tower top is 12.5 ℃. And (3) sampling and analyzing the content of high-boiling-point impurities at the top of the tower, wherein the content of the heptafluoro-n-butyronitrile is 0.13%, and other high-boiling-point impurities are not detected, extracting a gas phase at the top of the tower into a secondary adsorption column (an adsorbent is an F03 molecular sieve), wherein the content of the heptafluoro-n-butyronitrile at the outlet of the adsorption column is 0.05%, and extracting a product at the outlet of the adsorption column, cooling and storing the product in a low-temperature storage tank at the temperature of-. The product analysis results are shown in Table 1.
Example 3
In the same manner as in example 1, the crude gas pressure of the crude heptafluoroisobutyl gas was 0.4MPa, the gas flow rate was 0.5kg/h, and the space velocity was 100h-1And the gas enters a first-stage adsorption column (the filler is a 3A molecular sieve), the adsorbed heptafluoroisobutyronitrile gas enters a light component removal rectifying tower, the pressure in the light component removal rectifying tower is 0.11MPa, the temperature of a tower kettle is 20.8 ℃, and the temperature of a tower top is 18.5 ℃. The low boiling point impurity content in the tower kettle is sampled and analyzed, wherein the total content of oxygen and nitrogen is 0.02 percent, and the content of hexafluoropropylene is 0.06 percent. The product extracted from the tower bottom enters a heavy component removing rectifying tower, the pressure in the heavy component removing rectifying tower is 0.08MPa, and the tower bottomThe temperature was 17.3 ℃ and the overhead temperature was 13.5 ℃. And (3) sampling and analyzing the content of high-boiling-point impurities at the top of the tower, wherein the content of the heptafluoro n-butyronitrile is 0.10 percent, detecting other high-boiling-point impurities, extracting a gas phase at the top of the tower, allowing the gas phase to enter a secondary adsorption column (an adsorbent is coconut shell activated carbon), not detecting the content of the heptafluoro n-butyronitrile at the outlet of the sampling and analyzing adsorption column, cooling and storing a product extracted from the outlet of the adsorption column by a low-temperature storage tank at the temperature of-20 ℃. The product analysis results are shown in Table 1.
TABLE 1 test results of products
| Detecting items | Example 1 | Example 2 | Example 3 |
| Content of heptafluoroisobutyronitrile/%) | 99.8 | 99.6 | 99.9 |
| Oxygen + nitrogen/%) | 0.10 | 0.16 | 0.02 |
| CO2/％ | 0.01 | 0.03 | Not detected out |
| Hexafluoropropylene/%) | 0.04 | 0.12 | 0.06 |
| Heptafluoro-n-butyronitrile/%) | Not detected out | 0.05 | Not detected out |
| H2O/ppmv | 3.6 | 4.2 | 3.2 |
Claims (10)
1. A method for purifying heptafluoroisobutyronitrile is to obtain a heptafluoroisobutyronitrile product by adsorbing, rectifying and deeply adsorbing crude heptafluoroisobutyronitrile gas, and comprises the following steps:
(1) introducing the crude gas of heptafluoroisobutyronitrile into a first-stage adsorption column, and removing water and part of organic impurities;
(2) the adsorbed heptafluoroisobutyronitrile enters a light component removing rectifying tower to be continuously rectified to remove light component impurities, and the gas after light component removal enters a heavy component removing rectifying tower to remove heavy component impurities;
(3) and (3) the removed heptafluoroisobutyronitrile gas passes through a secondary adsorption column, the residual isomer heptafluoron-butyronitrile is removed by deep adsorption, and a heptafluoroisobutyronitrile product is collected.
2. The method of claim 1, wherein the raw gas of heptafluoroisobutyronitrile has a heptafluoroisobutyronitrile volume content of not less than 80%, wherein the impurities are mainly: (a) o is2、N2、CO2Light components such as perfluoroacetonitrile, perfluoropropionitrile, hexafluoropropylene and the like; (b) heptafluoro-n-butyronitrile, methyl trifluoroacetate and other heavy components; (c) h2O。
3. The method of claim 1, wherein the impurities removed from the top of the light ends distillation column are nitrogen, oxygen, carbon dioxide, hexafluoropropylene, C1-C3 subfluorides; the heavy component removed by the heavy component removing rectifying tower is most of heavy components such as heptafluoro-n-butyronitrile and methyl trifluoroacetate.
4. The method of claim 1, wherein the adsorbent in the first-stage adsorption column is silica gel, activated alumina, or a type A molecular sieve.
5. The method of claim 1, wherein the adsorption process conditions in step (1) are as follows: the temperature is 40-100 ℃, the pressure is 0.3-0.6 MPa, the gas flow is 0.1-10 kg/h, and the airspeed is 10-1000 h-1。
6. The method as claimed in claim 1, wherein the light component removal rectification tower in the step (2) has a tower pressure of 0.15-0.3 MPa, a tower kettle temperature of 20-30 ℃ and a tower top temperature of 15-25 ℃.
7. The method as claimed in claim 1, wherein in the step (2), when the content of the light components in the tower bottom of the light-weight-removing rectifying tower is less than 0.2%, the liquid phase at the bottom of the tower is transferred to the heavy-weight-removing rectifying tower.
8. The method as claimed in claim 1, wherein the heavy component removal rectification tower in the step (2) has a tower pressure of 0.05-0.15 MPa, a tower kettle temperature of 10-20 ℃ and a tower top temperature of 5-15 ℃.
9. The method as claimed in claim 1, wherein when the content of the top component of the heavy component removal rectifying tower in the step (2) is less than 0.2%, the gas phase of the top component enters the secondary adsorption column.
10. The method of claim 1, wherein the adsorbent in the secondary adsorption column is activated carbon or molecular sieve; the adsorption temperature is 20-30 ℃, the pressure is 0-0.15 MPa, the gas flow is 10-1000 g/h, and the space velocity is 10-300 h-1。
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112979499A (en) * | 2021-02-04 | 2021-06-18 | 北京宇极科技发展有限公司 | Separation method of mixed gas of heptafluoroisobutyronitrile and carbon dioxide |
| CN114105821A (en) * | 2020-08-28 | 2022-03-01 | 浙江省化工研究院有限公司 | Preparation method of heptafluoroisobutyronitrile |
| CN116120210A (en) * | 2022-12-29 | 2023-05-16 | 南通立洋化学有限公司 | Purification method for preparing acetonitrile by acetic acid ammoniation method and application thereof |
| CN116178211A (en) * | 2022-12-10 | 2023-05-30 | 昊华气体有限公司 | Method for removing high-content acidic impurities in perfluoroisobutyronitrile crude gas |
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| CN110526834A (en) * | 2019-09-20 | 2019-12-03 | 北京宇极科技发展有限公司 | A method of preparing high-purity perfluor isobutyronitrile |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114105821A (en) * | 2020-08-28 | 2022-03-01 | 浙江省化工研究院有限公司 | Preparation method of heptafluoroisobutyronitrile |
| CN114105821B (en) * | 2020-08-28 | 2023-09-12 | 浙江省化工研究院有限公司 | Preparation method of heptafluoroisobutyronitrile |
| CN112979499A (en) * | 2021-02-04 | 2021-06-18 | 北京宇极科技发展有限公司 | Separation method of mixed gas of heptafluoroisobutyronitrile and carbon dioxide |
| CN116178211A (en) * | 2022-12-10 | 2023-05-30 | 昊华气体有限公司 | Method for removing high-content acidic impurities in perfluoroisobutyronitrile crude gas |
| CN116120210A (en) * | 2022-12-29 | 2023-05-16 | 南通立洋化学有限公司 | Purification method for preparing acetonitrile by acetic acid ammoniation method and application thereof |
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