CN112899707A - Preparation method of hexafluoroethane - Google Patents
Preparation method of hexafluoroethane Download PDFInfo
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- CN112899707A CN112899707A CN202011059241.5A CN202011059241A CN112899707A CN 112899707 A CN112899707 A CN 112899707A CN 202011059241 A CN202011059241 A CN 202011059241A CN 112899707 A CN112899707 A CN 112899707A
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Abstract
The invention relates to a preparation method of hexafluoroethane, belonging to the technical field of fine fluorine chemical industry. Uniformly mixing hydrogen fluoride and alkali metal fluoride at the temperature of-30-0 ℃, adding an electrolysis raw material at the temperature of 0-5 ℃, carrying out an electrolysis reaction at the electrolysis temperature of-5-20 ℃ and the electrolysis voltage of 5-7V, collecting a gas-phase product generated by the electrolysis reaction by using a low-temperature cold trap, wherein the boiling point of the gas-phase product is-78 ℃, and preparing a crude hexafluoroethane product with the purity of more than 90%; further purification gave hexafluoroethane of purity greater than 99.5%. The method comprises the steps of preparing hexafluoroethane by using an electrolytic fluorination method by using alkali metal propionate as a raw material, hydrogen fluoride as a fluorination reagent and alkali metal fluoride as a conductive medium; the method has originality, nontoxic raw materials, low price and easy obtainment, a small amount of carbon tetrafluoride is used as a byproduct, other compounds with similar boiling points to chlorine compounds are not used, and the crude product is easy to purify to an electronic grade.
Description
Technical Field
The invention relates to a preparation method of hexafluoroethane, belonging to the technical field of fine fluorine chemical industry.
Background
The electronic gas is an indispensable basic supporting source material in the manufacturing process of integrated circuits, photoelectrons and microelectronics, particularly very large scale integrated circuits, liquid crystal display devices, semiconductor light emitting devices and semiconductor materials, is called blood and grain in the electronic industry, and the purity and cleanliness of the electronic gas directly influence the quality, the integration level, specific technical indexes and the yield of photoelectrons and microelectronic components and parts, and fundamentally restrict the accuracy and the precision of the circuits and the devices. In a chip manufacturing plant, a chip requires 2-3 months of process flow to complete 450 or more process steps to obtain chips with various circuit patterns. The process comprises a plurality of procedures of epitaxy, film forming, doping, etching, cleaning, packaging and the like, and high-purity electronic chemical gas and electronic mixed gas are required to be more than 30. The fluorine-containing electronic gas is mainly used as a cleaning agent and an etchant.
Hexafluoroethane, molecular formula: c2F6CAS number: 76-16-4, colorless and non-combustible gas under standard conditions, and the molecular weight is as follows: 138, boiling point: -78.2 ℃, melting point: -100.6 ℃, density: 7.534Kg/m3(24 ℃ C.); the relative density is 4.70 (air is 1), and the gas is nontoxic, colorless and tasteless under normal pressure. Hexafluoroethane is used as plasma etching gas and device surface cleaning agent in semiconductor and microelectronic industries, and can also be used for optical fiber production and low-temperature refrigerant. Hexafluoroethane is widely used in semiconductor manufacturing processes, for example, as an etchant, a cleaning gas after chemical vapor deposition, and a dry etching gas for silicon dioxide in plasma processes, because it is non-toxic, odorless, and highly stable. In recent years, with the rapid development of the semiconductor industry, the purity requirement of electronic gas is more and moreThe hexafluoroethane has the advantages of extremely tiny edge lateral erosion phenomenon, high etching rate and high accuracy, solves the problem that the conventional wet etching can not meet the high-accuracy fine line etching of a deep submicron integrated circuit with the thickness of 0.18-0.25 mu m, and well meets the process requirement of small line width. High purity hexafluoroethane has become an essential medium for very large scale integrated circuits and plays an important role in the development of the semiconductor industry.
At present, the preparation method of hexafluoroethane mainly comprises the following three methods:
1. fluorination of metal fluorides
Pentafluoroethane and metal fluorides (CoF)3，MnF3，AgF2) The reaction is carried out to prepare hexafluoroethane. For example, cobalt difluoride used as a catalyst is contacted with fluorine gas to react to generate cobalt trifluoride, and the cobalt trifluoride and pentafluoroethane react at 300-350 ℃ to prepare hexafluoroethane, wherein the chemical reaction formula is as follows:
2CoF2+F2→2CoF3，
CHF2CF3+2CoF3→CF3CF3+HF+2CoF2；
the method requires a high temperature, and incompletely reacted pentafluoroethane (b.p.: 48 ℃) remains in the product hexafluoroethane (b.p.: 78 ℃) and further purification to 5N or more is difficult.
2. Catalytic fluorination of hydrogen fluoride
Pentafluoroethane and chlorine gas are used for preparing pentafluoromonochloroethane under the condition of photoreaction, pentafluoromonochloroethane and hydrogen fluoride are used for preparing hexafluoroethane through liquid phase antimony fluoride catalysis, and the related chemical reaction formula is as follows:
CHF2CF3+Cl2→CClF2CF3+HCl，
CClF2CF3+HF→CF3CF3+HCl；
wherein the molar ratio of the pentafluorochloroethane to the hydrogen fluoride is 1:2, the contact time is 30s at the temperature of 50 ℃ and the reaction pressure of 3MPa, the content of hexafluoroethane in the obtained product is 63.72%, the content of the pentafluorochloroethane is 30.81%, and the content of the pentafluoroethane is 5.47%.
The reaction side reaction generates a plurality of chlorofluoroethanes which form azeotropic compounds with each other and cannot be separated, thus failing to meet the purity requirement of semiconductor gas.
3. Direct fluorination process
Acetylene or ethane directly reacts with fluorine gas for direct fluorination, and the related chemical reaction formula is as follows:
C2H2+4F2→C2F6+2HF，
C2H6+6F2→C2F6+6HF；
the method has the problems of large reaction heat release, equipment corrosion, explosion, easy C-C bond breakage, low generation rate and the like. In the direct fluorination method using fluorine gas, production and accumulation of carbon due to C — C bond cleavage or the like during a long-term reaction occur, and the generation and accumulation of carbon cause a risk of rapid reaction with fluorine gas or explosion.
Disclosure of Invention
In order to overcome the defects of a plurality of byproducts and difficult purification in the preparation of hexafluoroethane in the prior art, the invention aims to provide the preparation method of hexafluoroethane, which is simple, low in raw material toxicity and easy for separation and purification of products, wherein the purity of hexafluoroethane prepared by the method is more than 5N after purification, and the hexafluoroethane meets the requirements of semiconductor manufacture.
In order to achieve the purpose of the invention, the following technical scheme is provided.
A process for the preparation of hexafluoroethane, said process comprising the steps of:
hydrogen fluoride and alkali metal fluoride are evenly mixed at the temperature of minus 30 ℃ to 0 ℃, and then electrolytic raw materials are added at the temperature of 0 ℃ to minus 5 ℃ to carry out electrolytic reaction, wherein the electrolytic reaction conditions are as follows: the electrolysis temperature is-5-20 ℃, the electrolysis voltage is 5-7V, a gas-phase product generated by the electrolysis reaction is collected by using a low-temperature cold trap, the boiling point of the gas-phase product is-78 ℃, and a crude hexafluoroethane product is prepared, wherein the main component is hexafluoroethane, and the purity is more than 90%.
Preferably, the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride, sodium fluoride and lithium fluoride.
The electrolysis raw material is alkali metal propionate, preferably potassium propionate, sodium propionate or lithium propionate.
The low-temperature refrigerant can adopt liquid ammonia or dry ice, and preferably adopts liquid nitrogen.
The mass ratio of the hydrogen fluoride to the alkali metal fluoride to the electrolysis raw material is 70-90: 3-10: 5-20, and the mass ratio of the hydrogen fluoride to the alkali metal fluoride to the electrolysis raw material is preferably 85:5: 10.
The method relates to the following chemical reaction formula, wherein ECF is English abbreviation of electrochemical fluorination:
and washing the hexafluoroethane crude product by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain hexafluoroethane with the purity of more than 99.5%.
Advantageous effects
The invention provides a preparation method of hexafluoroethane, which takes alkali metal propionate as a raw material, hydrogen fluoride as a fluorination reagent and alkali metal fluoride as a conductive medium, and prepares hexafluoroethane by an electrolytic fluorination method; the method has originality, nontoxic raw materials, low price and easy obtainment, a small amount of carbon tetrafluoride is used as a byproduct, other compounds with similar boiling points to chlorine compounds are not used, and the crude product is easy to purify to an electronic grade.
Drawings
FIG. 1 is an infrared absorption spectrum of hexafluoroethane (10mmHg) prepared in example.
FIG. 2 is a gas chromatogram of the gas phase product prepared in example 1.
FIG. 3 is a gas chromatogram of the final product prepared in example 1.
FIG. 4 is a gas chromatogram of the final product prepared in example 2.
FIG. 5 is a gas chromatogram of the final product prepared in example 3.
Detailed Description
The present invention is further illustrated by the following detailed description, wherein the processes are conventional unless otherwise specified, and the starting materials are commercially available from a public perspective unless otherwise specified.
Example 1
A process for the preparation of hexafluoroethane, said process involving the chemical reaction formula:
(1) adding 8.5 kg of hydrogen fluoride and 0.5 kg of potassium fluoride into a 12L electrolytic cell, and uniformly mixing at-30 ℃;
(2) slowly adding 1 kg of potassium propionate to the electrolytic cell at-5 ℃;
(3) carrying out electrolytic reaction at 15 deg.C and 5V;
(4) collecting a gas-phase product generated by the electrolytic reaction by using a liquid nitrogen cold trap, wherein the boiling point of the gas-phase product is-78 ℃;
(5) and (4) washing the gas-phase product collected in the step (4) by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.
The gas phase products and end products described in this example were tested as follows:
as shown in FIG. 1, the gas sample was examined using the Sammerfei IS-10 infrared spectroscopy, demonstrating hexafluoroethane.
As shown in fig. 2, the agilent 7820 gas chromatography was used to detect the gas phase product, helium was used as the carrier gas, the column temperature was maintained at 60 ℃, the TCD detector was used, and the area normalization method was used to determine that the gas phase product was hexafluoroethane, and the purity was 93.7%.
As shown in fig. 3, the final product was hexafluoroethane with a purity of 99.8% as determined by using agilent 7820 gas chromatography with helium as carrier gas, maintaining the column temperature at 60 ℃, using a TCD detector, and using an area normalization method.
Example 2
A process for the preparation of hexafluoroethane, said process involving the chemical reaction formula:
(1) adding 9 kg of hydrogen fluoride and 0.5 kg of potassium fluoride into a 12L electrolytic cell, and uniformly mixing at-30 ℃;
(2) slowly adding 1 kg of sodium propionate to the electrolytic cell at-5 ℃;
(3) carrying out electrolytic reaction at 0 deg.C and 5V;
(4) collecting a gas-phase product generated by the electrolytic reaction by using a liquid nitrogen cold trap, wherein the boiling point of the gas-phase product is-78 ℃;
(5) and (4) washing the gas-phase product collected in the step (4) by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.
The gas phase products and end products described in this example were tested as follows:
as shown in FIG. 1, the gas sample was examined using the Sammerfei IS-10 infrared spectroscopy, demonstrating hexafluoroethane.
Detecting a gas phase product by using Agilent 7820 gas chromatography, taking helium as a carrier gas, keeping the column temperature at 60 ℃, using a TCD detector, and using an area normalization method, wherein the gas phase product is hexafluoroethane and the purity is 94.2%.
As shown in fig. 4, the final product was hexafluoroethane with a purity of 99.8% by using agilent 7820 gas chromatography with helium as carrier gas, maintaining the column temperature at 60 ℃, and a TCD detector using an area normalization method.
Example 3
A process for the preparation of hexafluoroethane, said process involving the chemical reaction formula:
(1) adding 8 kg of hydrogen fluoride and 0.5 kg of potassium fluoride into a 12L electrolytic cell, and uniformly mixing at-30 ℃;
(2) slowly adding 1.5 kg of lithium propionate to the electrolytic cell at 0 ℃;
(3) carrying out electrolytic reaction at 10 deg.C and 5V;
(4) collecting a gas-phase product generated by the electrolytic reaction by using a liquid nitrogen cold trap, wherein the boiling point of the gas-phase product is-78 ℃;
(5) and (4) washing the gas-phase product collected in the step (4) by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain a final product.
The gas phase products and end products described in this example were tested as follows:
as shown in FIG. 1, the gas sample was examined using the Sammerfei IS-10 infrared spectroscopy, demonstrating hexafluoroethane.
Detecting a gas phase product by using Agilent 7820 gas chromatography, taking helium as a carrier gas, keeping the column temperature at 60 ℃, using a TCD detector, and using an area normalization method, wherein the gas phase product is hexafluoroethane and the purity is 94%.
As shown in fig. 4, the final product was hexafluoroethane with a purity of 99.8% by using agilent 7820 gas chromatography with helium as carrier gas, maintaining the column temperature at 60 ℃, and a TCD detector using an area normalization method.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing hexafluoroethane, which is characterized in that: the method comprises the following steps:
uniformly mixing hydrogen fluoride and alkali metal fluoride at the temperature of-30-0 ℃, adding an electrolysis raw material at the temperature of 0-5 ℃, carrying out an electrolysis reaction at the electrolysis temperature of-5-20 ℃ and the electrolysis voltage of 5-7V, collecting a gas-phase product generated by the electrolysis reaction by using a low-temperature cold trap, wherein the boiling point of the gas-phase product is-78 ℃, and preparing a crude hexafluoroethane product with the purity of more than 90%;
the electrolysis raw material is alkali metal propionate;
the mass ratio of the hydrogen fluoride to the alkali metal fluoride to the electrolysis raw material is 70-90: 3-10: 5-20.
2. The process for producing hexafluoroethane as claimed in claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride, sodium fluoride and lithium fluoride.
3. The process for producing hexafluoroethane as claimed in claim 1, wherein: the electrolysis raw material is potassium propionate, sodium propionate or lithium propionate.
4. The process for producing hexafluoroethane as claimed in claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride, sodium fluoride and lithium fluoride;
the electrolysis raw material is potassium propionate, sodium propionate or lithium propionate.
5. The process for producing hexafluoroethane as claimed in claim 1, wherein: the mass ratio of hydrogen fluoride, alkali metal fluoride and electrolysis raw material was 85:5: 10.
6. The process for producing hexafluoroethane as claimed in claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride, sodium fluoride and lithium fluoride;
the electrolysis raw material is potassium propionate, sodium propionate or lithium propionate;
the mass ratio of hydrogen fluoride, alkali metal fluoride and electrolysis raw material was 85:5: 10.
7. The process for producing hexafluoroethane as claimed in claim 1, wherein: the low-temperature refrigerant is liquid ammonia or dry ice.
8. The process for producing hexafluoroethane as claimed in claim 1, wherein: the low-temperature refrigerant is liquid nitrogen.
9. The process for producing hexafluoroethane as claimed in claim 1, wherein: the alkali metal fluoride is at least one of potassium fluoride, cesium fluoride, sodium fluoride and lithium fluoride;
the electrolysis raw material is potassium propionate, sodium propionate or lithium propionate;
the mass ratio of the hydrogen fluoride to the alkali metal fluoride to the electrolysis raw material is 85:5: 10;
the low-temperature refrigerant is liquid ammonia or dry ice.
10. The process for producing hexafluoroethane as claimed in any one of claims 1 to 9, wherein: and washing the hexafluoroethane crude product by using a potassium hydroxide aqueous solution, drying by using a molecular sieve, and removing light components and heavy components by using a continuous rectifying tower to obtain hexafluoroethane with the purity of more than 99.5%.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114016061A (en) * | 2021-10-29 | 2022-02-08 | 中船重工（邯郸）派瑞特种气体有限公司 | Method and device for preparing octafluoropropane through electrolysis |
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| CN107604378A (en) * | 2017-10-19 | 2018-01-19 | 浙江巨圣氟化学有限公司 | A kind of preparation method of perfluor hexane |
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2020
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Patent Citations (8)
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| US3983015A (en) * | 1975-06-23 | 1976-09-28 | Phillips Petroleum Company | Electrochemical fluorination using excess current |
| CN1086551A (en) * | 1992-07-30 | 1994-05-11 | 明尼苏达矿产制造公司 | The bipolar system flow model electrolyzer and the method thereof that are used for electrochemical fluorination |
| US5573654A (en) * | 1994-03-04 | 1996-11-12 | Minnesota Mining And Manufacturing Company | Process for making hexafluoropropane and perfluoropropane |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114016061A (en) * | 2021-10-29 | 2022-02-08 | 中船重工（邯郸）派瑞特种气体有限公司 | Method and device for preparing octafluoropropane through electrolysis |
| CN114016061B (en) * | 2021-10-29 | 2023-09-08 | 中船(邯郸)派瑞特种气体股份有限公司 | Method and device for preparing octafluoropropane through electrolysis |
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