KR100543253B1 - Production and use of hexafluoroethane - Google Patents

Abstract

A mixed gas containing hexafluoroethane and chlorotrifluoromethane is reacted with gaseous hydrogen fluoride at 200 to 450 캜 in the presence of a fluorination catalyst to fluorine chlorotrifluoromethane, or having 1 to 3 carbon atoms. Preparation of high purity hexafluoroethane in which pentafluoroethane containing a chlorine compound is reacted with hydrogen in the gas phase in the presence of a hydrogenation catalyst at 150 to 400 ° C., and then the product is reacted with the gaseous fluorine in the presence of a diluent gas. Way.

Description

Method for producing and using hexafluoroethane {PRODUCTION AND USE OF HEXAFLUOROETHANE}

The present invention relates to a process for the preparation and use of hexafluoroethane.

Hexafluoroethane (CF ₃ CF ₃ ) is used, for example, as a cleaning gas or etching gas of semiconductors. As a manufacturing method of conventional CF ₃ CF ₃ ,

(1) an electrolytic fluorination method using ethane and / or ethylene as starting materials,

(2) a pyrolysis method for pyrolyzing tetrafluoroethylene,

(3) fluorinating acetylene, ethylene, and / or ethane using metal fluorides,

(4) dichlorotetrafluoroethane or chloropentafluoroethane using a hydrogen fluoride in the presence of a fluorination catalyst, and

(5) A direct fluorination method for reacting tetrafluoroethane and / or pentafluoroethane with fluorine is known.

However, when using the method of (4) above, for example, the produced CF ₃ CF ₃ contains impurities in the form of a compound derived from the starting raw material or a compound newly produced by the reaction. In particular, the problem is that such impurities contain chlorine compounds that are difficult to separate from CF ₃ CF ₃ .

For example, in the use of the method of (5), the produced CF ₃ CF ₃ also contains impurities in the form of a compound derived from the starting raw material or a compound newly produced by the reaction. These impurities also contain chlorine compounds that are difficult to separate from CF ₃ CF ₃ . Although the purification can be carried out to reduce the chlorine compound contained in the starting raw materials before the reaction with fluorine gas, conventionally known purification methods are often difficult to carry out industrially.

CF ₃ Chlorine compounds contained in CF ₃ include chloromethane, chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, Compounds, such as chlorotrifluoroethylene, are mentioned.

Among these chlorine compounds, chlorotrifluoromethane is difficult to separate because it forms an azeotrope with CF ₃ CF ₃ . The purification method of CF ₃ CF ₃ containing chlorotrifluoromethane contains impurities such as, for example, trifluoromethane (CHF ₃ ) and chlorotrifluoromethane (CClF ₃ ) described in US Pat. No. 5,523,499. CF _{3 to} CF ₃ by contacting with an adsorbent such as activated carbon or molecular sieve (molecular sieve) comprises a method for adsorption and removal of impurities.

The purification method using the adsorbent will vary depending on the content of impurities, but in the case of normal operation, special equipment is required for regenerating the adsorbent at almost constant intervals. For example, in a method of alternately operating two adsorption towers, adsorbing impurities and regenerating adsorbents, a large amount of gas can be continuously processed, but adsorption-free chlorotrifluoromethane Because this is a particular freon associated with the ozone depletion, it cannot be released directly into the atmosphere, so several methods must be used to make it harmless.

On the other hand, pentafluoroethane (CF ₃ CHF ₂ ) is used, for example, as a starting material for the preparation of low temperature refrigerant or hexafluoroethane (CF ₃ CF ₃ ). The following methods are known as a manufacturing method of the pentafluoroethane conventionally.

(1) A method of fluorinating perchloroethylene (CCl ₂ = CCl ₂ ) or its fluoride with hydrogen fluoride (Japanese Patent Laid-Open No. 8-268932, Japanese Patent Laid-Open No. 9-511515).

(2) A method of hydrocracking chloropentafluoroethane (CClF ₂ CF ₃ ) (Japanese Patent No. 2540409).
(3) A method of reacting fluorine gas with halogen-containing ethylene (Japanese Patent Laid-Open No. 1-38034).

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When the above production method is used, the main impurity in pentafluoroethane as a target is a chlorine compound in which a chlorine atom is naturally contained in a molecule. Examples of the chlorine compound include compounds having one carbon atom such as chloromethane, chlorodifluoromethane and chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane and chlorotrifluoroethane. Unsaturated compounds, such as a compound with two carboato atoms and chlorotrifluoroethylene, are mentioned.

When hexafluoroethane is produced by directly fluorination of pentafluoroethane and fluorine gas (F ₂ ), any chlorine compound contained in pentafluoroethane reacts with fluorine gas to provide chlorine, hydrogen chloride, chlorine fluoride, Or produce different types of chlorofluorocarbons. While the perfluorocarbons (PFCs) contained in pentafluoroethane show no particular problem, chloromethane (CH ₃ Cl) and chlorodifluoromethane (CHClF ₂ ) react with fluorine gas to give chlorotrifluoro Methane (CClF ₃ ) is produced. Since hexafluoroethane and chlorotrifluoromethane form an azeotropic mixture, it is difficult to remove chlorotrifluoromethane even if distillation or adsorptive purification is performed. Therefore, in the case of producing hexafluoroethane by reacting pentafluoroethane and fluorine gas, it is preferable to use a very small amount of chlorine compound and pentafluoroethane.

In the conventional method for producing pentafluoroethane, the content of the chlorine compound contained in pentafluoroethane may be about 1 vol% in total. Thus, repetitive distillation is considered to remove chlorine compounds contained in pentafluoroethane, resulting in higher yields of pentafluoroethane, but this operation is not economical due to distillation losses and rising distillation production costs. On the other hand, some of the chlorine compounds form an azeotrope or azeotrope-like mixture with pentafluoroethane, which leads to a situation in which it is extremely difficult to separate the chlorine compounds by only distillation alone. In particular, chloropentafluoroethane (CClF ₂ CF ₃ ) is usually contained in pentafluoroethane at concentrations of several thousand ppm or more, but since the pentafluoroethane and chloropentafluoroethane form an azeotropic mixture, conventional separation and Separation is difficult by the distillation operation used in the purification method.

Disclosure of the Invention

SUMMARY OF THE INVENTION The object of the present invention is achieved under the above-mentioned background, a method of industrially advantageously producing high-purity hexafluoroethane that can be used as an etching gas or a cleaning gas in the manufacturing process of a semiconductor device, and the high-purity hexafluoro obtained accordingly. To provide the use of roethane.

The present inventors have made diligent efforts to solve the above-mentioned problems. As a result, the above problems are solved by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane with hydrogen fluoride in a gaseous phase at a predetermined temperature in the presence of a fluorination catalyst. The present invention has been completed and found that it can be solved by using a process of fluorinating trifluoromethane.

Accordingly, the present invention includes a step of fluorinating chlorotrifluoromethane by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane with gaseous hydrogen fluoride at 200 to 450 캜 in the presence of a fluorination catalyst. Provided are methods for preparing hexafluoroethane.

The present invention provides a method for producing hexafluoroethane, further comprising the following steps (1) and (2):

(1) fluorinated chlorotrifluoromethane by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane with hydrogen gaseous fluoride in the presence of a fluorination catalyst at 200 to 450 캜, followed by tetrafluoromethane. Process to convert.

(2) A step of distilling a mixed gas containing tetrafluoromethane and hexafluoroethane obtained in step (1) to obtain purified hexafluoroethane.

The present invention further provides a hexafluoroethane product containing hexafluoroethane having a purity of at least 99.9997 vol% and obtained using the above production method.

The present invention further provides a cleaning gas containing the hexafluoroethane product.

As a result of our research efforts, the above-mentioned problems are solved by a process of hydrogenating a chlorine compound by reacting pentafluoroethane containing a chlorine compound having 1 to 3 carbon atoms at a predetermined temperature with hydrogen in a gaseous phase in the presence of a hydrogenation catalyst ( The present invention has been found to be solved by using step 1) and step (2) in which the product of step (1) is reacted with gaseous fluorine in the presence of diluent gas to produce hexafluoroethane.

Accordingly, the present invention provides a process (1) for hydrogenating a chlorine compound by reacting pentafluoroethane containing a chlorine compound having 1 to 3 carbon atoms at 150 to 400 ° C. with hydrogen in a gaseous phase in the presence of a hydrogenation catalyst; A method for producing hexafluoroethane comprising the step (2) of reacting the product of 1) with gaseous fluorine in the presence of a diluent gas to produce hexafluoroethane.

The present invention further provides a hexafluoroethane product containing hexafluoroethane with a purity of at least 99.9997 vol%, obtained using the above production method.

The present invention further provides an etching gas containing the above hexafluoroethane product.

The present invention further provides a cleaning gas containing the hexafluoroethane product.
Embodiment of invention

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Hereinafter, the method for producing hexafluoroethane according to the first aspect of the present invention will be described in detail.

As mentioned above, the manufacturing method of various hexafluoroethane is known conventionally. Industrially safe and economical methods include:

(1) A method in which dichlorotetrafluoroethane or chloropentafluoroethane is fluorinated using hydrogen fluoride in the presence of a fluorination catalyst.

(2) A method of reacting tetrafluoroethane and / or pentafluoroethane with fluorine gas.

In the above (1) and (2), compounds such as dichlorotetrafluoroethane, chloropentafluoroethane or pentafluoroethane used as starting materials are, for example, tetrachloroethylene (CCl ₂ = CCl) as starting materials. ₂ ), and compounds such as tetrafluoroethane may be prepared using trichloroethylene (CHCl = CCl ₂ ) as a starting material. However, irrespective of the production method used, the produced hexafluoroethane contains chlorine compounds derived from starting materials as impurities, and the content of impurities tends to increase as the reaction temperature increases.

For example, in the pentafluoroethane (CF ₃ CHF ₂ ) commercially available as a refrigerant, such a chlorine compound is contained as an impurity. When CF ₃ CF ₃ is prepared by direct fluorination of pentafluoroethane containing a chlorine compound with fluorine gas, chlorine, hydrogen chloride, chlorine and Several kinds of chlorofluorocarbons are produced. For example, chlorodifluoromethane contained as an impurity reacts with fluorine gas to produce chlorotrifluoromethane. Chlorotrifluoromethane forms an azeotropic mixture with CF ₃ CF ₃ and is therefore a compound that is extremely difficult to separate after distillation.

In the method for producing hexafluoroethane according to the first aspect of the present invention, a mixed gas containing chlorotrifluoromethane and hexafluoroethane, which is extremely difficult to separate, is mixed with gaseous hydrogen fluoride in the presence of a fluorination catalyst at 200 to 450 ° C. Reacting in a fluorinated chlorotrifluoromethane. The mixed gas contains at least 99.9 vol% hexafluoroethane while also containing chlorotrifluoromethane as impurities.

As the fluorination catalyst used in the above production method, trivalent chromium oxide is a main component, and it is preferable to use a catalyst containing nickel, zinc, indium and / or gallium in an amount of 0.01 to 0.6 with respect to chromium in an atomic ratio. The catalyst may be in the form of a supported catalyst or a bulk catalyst. In the case of the supported catalyst, activated carbon, alumina, partially fluorinated alumina, and the like are preferred, and the component loading rate is preferably 30 wt% or less.

The temperature at which the mixed gas containing hexafluoroethane and chlorotrifluoromethane is reacted with hydrogen fluoride in the presence of a fluorination catalyst is 200 to 450 캜, preferably 250 to 400 캜. If the reaction temperature is lower than 200 ° C., chlorotrifluoromethane is not easily fluorinated. If the reaction temperature is higher than 450 ° C., the catalyst life is shortened and impurities tend to increase.

In the fluorination reaction, the molar ratio of hydrogen fluoride and mixed gas (mixed gas containing hydrogen fluoride / hexafluoroethane and chlorotrifluoromethane) is preferably in the range of 0.05 to 10, and more preferably in the range of 0.05 to 5. . When the molar ratio of hydrogen fluoride and mixed gas is less than 0.05, various reactions tend to be easily generated by side reactions. If the molar ratio is greater than 10, the reactor must be large and the unreacted hydrogen fluoride should be recovered. The problem arises economically undesirable.

 The concentration of chlorotrifluoromethane contained in the mixed gas is preferably 0.1 vol% or less, more preferably 0.05 vol% or less.

The mixed gas is preferably obtained by reacting dichlorotetrafluoroethane and / or chloropentafluoroethane with gaseous hydrogen fluoride in the presence of a fluorination catalyst. Alternatively, the mixed gas may be obtained by reacting tetrafluoroethane and / or pentafluoroethane with fluorine gas.

The method for producing hexafluoroethane according to the first aspect of the present invention may include the following steps (1) and (2).

(1) fluorinated chlorotrifluoromethane by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane with hydrogen gaseous fluoride in the presence of a fluorination catalyst at 200 to 450 캜, followed by tetrafluoromethane. Process to convert.

(2) A step of distilling a mixed gas containing tetrafluoromethane and hexafluoroethane obtained in step (1) to obtain purified hexafluoroethane.

As shown by the following formula (1), chlorotrifluoromethane is reacted with hydrogen fluoride in the presence of a fluorination catalyst to produce tetrafluoromethane (CF ₄ ).

CF₄ + HCl (1)CClF ₃ + HF

CF ₄ + HCl (1)

Instead of hexafluoroethane, impurity chlorotrifluoromethane is reacted with hydrogen fluoride. Since the boiling point difference between the produced CF ₄ and the unreacted residue CF ₃ CF ₃ is about 50 ° C., CF ₄ and CF ₃ CF ₃ do not form an azeotrope but can be easily separated by a known distillation operation. .

The fluorinated catalyst of step (1) is preferably a supported catalyst or bulk catalyst whose main component is trivalent chromium oxide.

In step (1), the molar ratio of hydrogen fluoride and mixed gas (mixed gas containing hydrogen fluoride / hexafluoroethane and chlorotrifluoromethane) is preferably in the range of 0.05 to 10, and the mixed gas of step (1) The concentration of chlorotrifluoromethane contained therein is preferably 0.1 vol% or less.

The mixed gas of step (1) is preferably obtained by reacting dichlorotetrafluoroethane and / or chloropentafluoroethane with hydrogen fluoride in the gas phase in the presence of a fluorination catalyst. Alternatively, the mixed gas of step (1) can be obtained by reacting tetrafluoroethane and / or pentafluoroethane with fluorine gas.

As a method of removing the acid component which consists of hydrochloric acid and excess hydrogen fluoride produced | generated by reaction of the said Formula (1), the method of contacting with a tableting agent, the method of contacting with water, or aqueous alkali solution, etc. Can be mentioned. After removing the acid component, the gas containing CF ₃ CF ₃ as a main component can be dehydrated using a dehydrating agent such as zeolite, and then subjected to a distillation operation to remove a low boiling point portion, thereby obtaining high purity CF ₃ CF ₃ .

Hereinafter, the method for producing hexafluoroethane according to the second aspect of the present invention will be described in detail.

This production method comprises the steps (1) of hydrogenating a chlorine compound by reacting pentafluoroethane containing a chlorine compound having 1 to 3 carbon atoms at 150 to 400 ° C. with hydrogen in a gaseous phase in the presence of a hydrogenation catalyst; A method for producing hexafluoroethane comprising the step (2) of reacting a product of) with gaseous fluorine in the presence of a dilution gas to produce hexafluoroethane.

As described above, pentafluoroethane used in the preparation method is generally prepared by fluorination of perchloroethylene (CCl ₂ = CCl ₂ ) or its fluoride with hydrogen fluoride (HF), the pentafluoroethane starting As a chlorine compound derived from a raw material, chloromethane, chlorodifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, chlorotrifluoroethylene, etc. are contained. Known distillation operations can be used to purify pentafluoroethane containing these compounds with high purity, but since the chlorine compound and pentefluoroethane form an azeotropic or azeotrope-like mixture, their separation and purification are extremely difficult. Therefore, it is necessary to increase the number of stages and the number of distillation columns of the distillation column, and thus, the installation cost and the energy cost are added, which is economically problematic.

In the above production method, a chlorine compound containing a chlorine atom and contained as an impurity in pentafluoroethane is reacted with hydrogen in a gaseous phase at 150 to 400 ° C. in the presence of a hydrogenation catalyst, and then hydrogenated, followed by hydrofluorocarbons (HFC). It starts from the process (1) which switches to etc. For example, hydrogenating chloropentafluoroethane (CF ₃ CClF ₂ ) and chlorotetrafluoroethane (CF ₃ CHClF) contained as impurities in pentafluoroethane by hydrogen, the following formulas (2) and (3) Reaction occurs in.

CF₃CHF₂ + HCl (2)CF ₃ CClF + H ₂

CF ₃ CHF ₂ + HCl (2)

CF₃CH₂F + HCl (3)CF ₃ CHClF + H ₂

CF ₃ CH ₂ F + HCl (3)

The products are hydrofluorocarbons containing no chlorine atom, and hydrochloric acid is produced as a by-product.

Compounds converted into hydrofluorocarbons by the hydrogenation reaction include chloromethane, chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, Chlorotrifluoroethane, chlorotrifluoroethylene, and the like, and these compounds are usually contained in pentafluoroethane in a total amount of thousands or more volppm or more. When pentafluoroethane containing the compound is directly reacted with fluorine gas, the methane compound is mainly converted into chlorotrifluoromethane, while the ethane compound is mainly converted into chloropentafluoroethane. Hexafluoroethane obtained after the reaction contains chlorotrifluoromethane and chloropentafluoroethane as main impurities.

Chloropentafluoroethane virtually does not react with fluorine gas at low temperatures. As a result of the study by the inventors, for example, when the reaction temperature is 400 ° C. and the concentration of chloropentafluoroethane in pentafluoroethane is about 800 volppm or less, the chloropentafluoroethane is split and chlorotrifluoromethane. Although the amount of was less than 1 volppm, when the concentration of chloropentafluoroethane exceeded about 2000 volppm, it was found that about 2 volppm was produced.

Since chlorotrifluoromethane forms an azeotrope with hexafluoroethane, it is a compound which is difficult to remove by distillation or adsorption operation even at low concentration. Therefore, it is preferable not only to remove the compound which produces chlorotrifluoromethane by reaction with fluorine gas from pentafluoroethane which is a starting material, but also to reduce content of chloropentafluoroethane to low concentration as possible.

The amount of the chlorine compound contained in pentafluoroethane used in this production method is preferably 1 vol% or less, more preferably 0.5 vol% or less, even more preferably 0.3 vol% or less. If the content of the chlorine compound exceeds 1 vol%, it is necessary to increase the reaction temperature, which will probably shorten the life of the hydrogenation catalyst.

The hydrogenation catalyst of step (1) is preferably a catalyst containing one or more elements selected from platinum group elements such as platinum, palladium, rhodium, iridium, ruthenium and osmium, and these metals or metal oxides or salts as starting materials. Can be used. Examples of the carrier that can be used for the catalyst include activated carbon, alumina, fluorinated alumina, and the like, and in order for the desired reaction to proceed efficiently, the element component-support ratio is preferably at least 0.02 wt%. The hydrogenation catalyst can be prepared, for example, by dissolving a metal salt in an aqueous solvent such as water, methanol or acetone, and then immersing the carrier in a solution to adsorb the necessary elements, then removing the solvent and subjecting it to heat reduction with hydrogen or the like. Can be.

The reaction temperature of the hydrogenation reaction of process (1) is 150-400 degreeC, Preferably it is 200-300 degreeC. If the reaction temperature is higher than 400 ° C., the catalyst life tends to be shortened, and often the excess reaction proceeds. The progress of the excess hydrogenation reaction is not preferable because 1,1,1-trifluoroethane and the like are produced. In the step (2) in which the organic compound and the fluorine gas are directly involved in the fluorination reaction, since a large amount of heat of reaction is generated, for example, the number of CH bonds in the organic compound substrate replaced with CF bonds increases, so that the heat of reaction increases. It is difficult to control the reaction because there is a tendency for local heating portions (hot spots) to be formed. As a result, it is preferable to use pentafluoroethane containing extremely small amounts of hydrofluorocarbons (HFCs) and especially 1,1,1-trifluoroethane having a large number of C-H bonds. On the other hand, when reaction temperature is less than 150 degreeC, it exists in the tendency for progress of a desired reaction to be inhibited.

In the hydrogenation reaction of step (1), the molar ratio of hydrogen and mixed gas (mixed gas containing hydrogen / chlorine compound and pentafluoroethane) is preferably in the range of 1 to 20, more preferably in the range of 2 to 10. good. Preferred reaction pressures range from atmospheric pressure to 1.5 MPa. If the reaction pressure exceeds 1.5 MPa, this may be a problem because a pressure resistant device is required.

In the above production method, step (1) is carried out under the reaction conditions described above, and the reaction product is hydrofluorocarbons containing no chlorine atoms other than pentafluoroethane, and a small amount of unreacted chlorine compounds and hydrochloric acid as by-products. It will contain preferred acid components such as to be removed.

As the method of removing the acid component, for example, a method of contacting with a tablet or a method of contacting with water or an aqueous alkali solution can be used. The gas from which the acid component has been removed is preferably dehydrated with a dehydrating agent such as zeolite, followed by distillation prior to the direct fluorination step to obtain purified pentafluoroethane, and unreacted hydrogen is preferably separated. Since hydrogen can react violently with fluorine gas, it is preferable that hydrogen is not mixed in the direct fluorination reaction of step (2).

The chlorine compound contained in the mixed gas obtained in the step (1) is preferably present in an amount of 0.05 vol% or less in total, and 1,1,1-trifluoroethane is preferably present in 0.2 vol% or less.

Hereinafter, the process (2) which makes the gas containing pentafluoroethane obtained through process (1) as a main component and react with fluorine gas is demonstrated.

Step (2) is carried out in the presence of diluent gas in order to set the concentration of the mixed gas containing pentafluoroethane as the main component to be below the explosion range. Specifically, the concentration of pentafluoroethane at the reactor inlet is preferably about 6 mol% or less. The diluent gas used contains at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane and hydrogen fluoride, and it is preferable to use a diluent gas rich in hydrogen fluoride. Diluent gas rich in hydrogen fluoride means a diluent gas containing 50 mol% or more of hydrogen fluoride.

The amount of fluorine gas used is in the molar ratio to the mixed gas containing pentafluoroethane as a main component (pentafluoroethane containing F ₂ / hydrogenated compounds) in the range of 0.5 to 2.0, preferably in the range of 0.9 to 1.3. . The reaction temperature is preferably 250 to 500 ° C, more preferably 350 to 450 ° C. If the reaction temperature is higher than 500 ° C., the desired product hexafluoroethane may be cleaved to produce tetrafluoromethane (CF ₄ ). If the reaction temperature is less than 250 ° C., the reaction rate may be slow.

There is no particular limitation on the method for purifying the gas flowing out after the step (2), but it is preferable to first remove the remaining unreacted fluorine gas. For example, hydrofluorocarbons such as trifluoromethane can be added to react with excess fluorine gas to be removed. Subsequently, distillation, for example, first distillation of hydrogen fluoride and organic matter is preferred. The separated hydrogen fluoride can be reused in the direct fluorination reaction of process (2) as a diluent gas or utilized for other purposes.

The composition of the gas containing the separated organic matter will depend greatly on the diluent gas used in the reaction. For example, when a gas containing hydrogen fluoride or hexafluoroethane itself is used as the diluent gas, The produced gas contains hexafluoroethane as a main component. When tetrafluoromethane or octafluoropropane is used as the diluent gas, further distillation is performed to purify, but in any case, high purity hexafluoroethane can be obtained by repeatedly distilling the generated mixed gas. have.

The distillation and purification of the mixed gas obtained by the above reaction depends on the composition ratio, but as an example, a low boiling point component such as an inert gas and tetrafluoromethane is extracted from the top of the first distillation column, and hexafluorine is used. A mixed gas containing roethane as a main component is extracted from the bottom. Subsequently, the mixed gas extracted from the bottom of the column is introduced into the second distillation column, and low boiling point components such as inert gas and trifluoromethane are extracted from the top of the second distillation column, and then hexafluoro extracted from the bottom of the column. Distillation is complete | finished by introduce | transducing the mixed gas which has a loethane as a main component to a 3rd distillation column, and extracting high purity hexafluoroethane from the tower part.

The above-described preparation method of the present invention can be used to obtain hexafluoroethane having a purity of 99.9997 vol% or more. Therefore, chlorotrifluoromethane contained as impurities is less than 1 volppm. CF ₃ CF ₃ with a purity of 99.9997 vol% or more is determined using gas chromatography (GC) methods such as TCD, FID (both precut methods), ECD or gas chromatography mass spectrometer (GC-MS) Can be analyzed.

Hereinafter, the use of the high purity hexafluoroethane obtained using the manufacturing method of this invention is demonstrated. High purity CF ₃ CF ₃ or a mixture of high purity CF ₃ CF ₃ and an inert gas such as He, N ₂ and Ar, or a gas such as O ₂ and NF ₃ (according to the object of the present invention, these are “hexafluoroethane products” May be used as an etching gas for an etching process in a semiconductor device manufacturing process or a cleaning gas for a cleaning process in a semiconductor device manufacturing process. In the manufacturing processes of semiconductor devices such as LSI and TFT, thin films and thick films are formed by CVD, sputtering, vapor deposition, and the like, and are etched to form circuit patterns. The device forming the thin film and the thick film should be cleaned to remove unnecessary deposits deposited on the inner wall of the device, jigs, and the like. Unnecessary buildup is the cause of particle generation and needs to be removed from time to time to produce high quality membranes.

The etching method using CF ₃ CF ₃ can be carried out under various dry etching conditions such as plasma etching, microwave etching, etc. In this case, CF ₃ CF ₃ is an inert gas such as He, N ₂ or Ar, or HCl, O ₂ , H ₂ , F ₂ , NF ₃ and the like can be used by mixing with a suitable ratio of gas.

The present invention will be described in detail by the following examples. However, the scope of the present invention is not limited by these Examples.

Preparation Example 1 of Pentafluoroethane (Starting Material Example 1)

Tetrachloroethylene (CCl ₂ = CCl ₂ ) was contacted with molecular sieve 4A (manufactured by Union Showa Co., Ltd.) to remove stabilizer and water in tetrachloroethylene, and then hydrogen fluoride (HF) in the presence of a chromium-based fluorination catalyst. [First reaction: reaction pressure 0.4 MPa, reaction temperature 320 ° C., HF / tetrachloroethylene = 8 (molar ratio)]. Next, a mixed gas mainly containing chlorotrifluoroethane (CF ₃ CHCl ₂ ) and chlorotetrafluoroethane (CF ₃ CHClF) obtained in the first reaction was reacted with hydrogen fluoride [second reaction: reaction pressure 0.45 MPa, reaction temperature 330 ° C., HF / (CF ₃ CHCl ₂ + CF ₃ CHClF) = 6 (molar ratio)]. After completion of the second reaction, an acid component was removed using a known method, and distillation purification was performed to obtain an effluent containing pentafluoroethane as a main component. This effluent was analyzed by gas chromatography to confirm that it was pentafluoroethane having the composition shown in Table 1 below.

Preparation Example 1 of Starting Raw Material Hexafluoroethane (Starting Raw Material Example 2)

Inconel 600 reactor with an internal diameter of 20.6 mm and a length of 500 mm (electric heater heating method: passivated with fluorine gas at a temperature of 500 ° C.) at a flow rate of 30 NL / hr from the two gas inlets in a total flow rate of nitrogen gas Was introduced and the reactor internal temperature was maintained at 380 ° C. Next, hydrogen fluoride was flowed through the two gas inlets at a total flow rate of 50 NL / hr, and pentafluoroethane obtained in Production Example 1 of pentafluoroethane from either gas inlet. Example 1) was flowed at a flow rate of 3.6 NL / hr. From the other gas inlet, fluorine gas was introduced at a flow rate of 3.9 NL / hr for fluorination reaction. The outlet gas of the reactor was contacted with an aqueous potassium hydroxide solution and an aqueous potassium iodide solution to remove hydrogen fluoride and unreacted fluorine gas in the outlet gas. After contacting with a dehydrating agent to dry, the dried gas was purified by cooling, trapping and distillation. Purified hexafluoroethane was analyzed by gas chromatography, and the results are shown in Table 2 below.

Preparation Example 1 of Catalyst (Catalyst Example 1)

0.6 L of pure water was added to a 10 L vessel, followed by stirring. Then, 1.2 L of pure water was added to 452 g of Cr (NO ₃ ) ₃ 9H ₂ O and In (NO ₃ ) ₃ ㆍ nH ₂ O (where n is Solution of 42 g and 0.31 L of 28% ammonia water were added dropwise for about 1 hour while controlling the flow rates of the two aqueous solutions so that the pH of the reaction solution was in the range of 7.5 to 8.5. The obtained slurry was separated by filtration, and the solid separated by filtration was sufficiently washed with pure water and then dried at 120 ° C for 12 hours. The dried solid was pulverized, then mixed with graphite and pelleted by a tableting machine. This pellet was calcined at 400 ° C. for 4 hours under a stream of nitrogen to prepare a catalyst precursor. This catalyst precursor was then charged to an Inconel reactor and subjected to fluorination treatment (catalyst activation) under a hydrogen fluoride stream diluted with nitrogen at 350 ° C. under atmospheric pressure. Then, a catalyst (catalyst example 1) was prepared by performing a fluorination treatment (catalytic activation) at 400 ° C. under a 100% hydrogen fluoride stream, followed by a nitrogen fluoride stream.

Example 1

An Inconel 600 reactor having an internal diameter of 1 inch and a length of 1 m was charged with 150 ml of the catalyst (catalyst example 1) obtained in Preparation Example 1 of the catalyst, and the temperature was maintained at 280 ° C while passing through nitrogen gas. Hydrogen fluoride was then supplied at 1.5 NL / hr, and hexafluoroethane (starting raw material example 2), which was a starting material of the composition shown in Table 2, was supplied at 3.5 NL / hr. Then, the supply of nitrogen gas was stopped and reaction was started. After 3 hours, the outlet gas of the reactor was washed with aqueous potassium hydroxide solution to remove the acid component, and the composition of the gas was analyzed by gas chromatography to confirm that it was hexafluoroethane having the composition shown in Table 3 below.

As shown in Table 3 above, chlorotrifluoromethane contained in hexafluoroethane can be converted to tetrafluoromethane.

Then, the reaction was carried out to remove the acid component, the gas was brought into contact with a dehydrating agent, dried, cooled and collected, and then purified by distillation by a known method. Hexafluoroethane obtained by distillation was analyzed by gas chromatography, and the results are shown in Table 4 below.

As a result of the analysis shown in Table 4, the purity of hexafluoroethane was 99.9997 vol% or more, and the content of chlorotrifluoromethane was less than 0.5 volppm. Impurities were analyzed by gas chromatography using TCD, FID, ECD and GC-MS.

Example 2

An Inconel 600 reactor having an internal diameter of 1 inch and a length of 1 m was charged with 100 ml of the catalyst obtained in Preparation Example 1 of Catalyst (Catalyst Example 1), and the temperature was maintained at 400 ° C. while passing nitrogen gas. Then, hydrogen fluoride was supplied at 10 NL / hr, and hexafluoroethane (starting raw material example 2), which was a starting material of the composition shown in Table 2, was supplied at 10 NL / hr. Thereafter, the supply of nitrogen gas was stopped and the reaction was started. After 3 hours, the outlet gas of the reactor was treated in the same manner as in Example 1 to remove the acid component, and then analyzed by gas chromatography. As a result, the product was confirmed to be hexafluoroethane of the composition shown in Table 5 below.

In the said Table 5, ND shows "below the detection limit" in GC-MS, and it means that it is less than 0.1 volppm as a numerical value. Therefore, content of CClF ₃ is less than 0.1 volppm.

Hexafluoroethane obtained by cooling, trapping and distilling the product gas dehydrated in the same manner as in Example 1 was analyzed by gas chromatography to obtain the results shown in Table 6 below.

As the analytical results in Table 6 clearly show, the content of CCl ₃ F is less than 0.1 volppm, thus high purity hexafluoroethane can be obtained.

Preparation Example 2 of Pentafluoroethane (Starting Material Example 3)

Tetrachloroethylene (CCl ₂ = CCl ₂ ) was contacted with molecular sieve 4A (manufactured by Union Showa Co., Ltd.) to remove stabilizer and water in tetrachloroethylene, and then hydrogen fluoride (HF) in the presence of a chromium-based fluorination catalyst. Reacted with [First reaction: reaction pressure 0.4 MPa, reaction temperature 300 ° C., HF / tetrachloroethylene = 8 (molar ratio)]. Next, a mixed gas containing dichlorotrifluoroethane (CF ₃ CHCl ₂ ) and chlorotetrafluoroethane (CF ₃ CHClF) mainly obtained in the first reaction was reacted with hydrogen fluoride [second reaction: reaction pressure 0.45 MPa, reaction temperature 330 ° C., HF / (CF ₃ CHCl ₂ + CF ₃ CHClF) = 6 (molar ratio)]. After the completion of the second reaction, an acid component was removed using a known method, and distillation purification was performed to obtain an effluent containing pentafluoroethane as a main component. Next, this effluent was analyzed by gas chromatography, and it confirmed that it was a mixed gas (starting raw material example 3) of the composition shown in following Table 7.

Preparation Example 3 of Pentafluoroethane (Starting Material Example 4)

The mixed gas (starting raw material example 3) containing pentafluoroethane obtained by the above-mentioned manufacturing method as a main component was distilled using a well-known method. The effluent was analyzed by gas chromatography to confirm that it was a mixed gas (starting material example 4) having the composition shown in Table 8 below.

Preparation Example 2 of Catalyst (Catalyst Example 2)

Sodium palladium chloride was dissolved in water, and a 1.6 mm phi spherical alumina carrier was immersed therein to adsorb the palladium salt. Then, the solvent was removed at a temperature of 100 deg. C, followed by air firing at 300 deg. Next, hydrogen reduction was performed at 350 ° C. The supporting ratio of the obtained palladium catalyst was 2.0%.

Preparation Example 3 of Catalyst (Catalyst Example 3)

The platinum chloride was dissolved in water, the 1.6 mm φ spherical alumina carrier was immersed to adsorb the platinum salt, the solvent was removed at a temperature of 100 ° C, air fired at 300 ° C, and then hydrogen reduced at 350 ° C. Was performed. The supporting ratio of the obtained platinum catalyst was 2.0%.

Example 3

An Inconel 600 reactor having an internal diameter of 1 inch and a length of 1 m was charged with 100 ml of the catalyst obtained in Preparation Example 2 (Catalyst Example 2), and the temperature was maintained at 280 ° C while passing through nitrogen gas. Then, hydrogen was supplied at 0.36 NL / hr, a mixed gas having a composition shown in Table 7 (starting material example 3) was supplied at 8.33 NL / hr, and then the supply of nitrogen gas was stopped and the reaction was carried out [Step (1) )]. After 2 hours, the outlet gas of the reactor was washed with aqueous potassium hydroxide solution to remove the acid component, and then the composition of the gas was analyzed by gas chromatography, and the mixed gas mainly containing pentafluoroethane having the composition shown in Table 9 below. It was confirmed that.

The mixed gas containing pentafluoroethane of the composition shown in Table 9 obtained according to the above-mentioned manufacturing method as a main component is distilled using a well-known method, and after removing low boiling point components, such as an inert gas and hydrogen gas, fluorine gas Direct fluorination reaction [step (2)] was performed.

Nitrogen gas was introduced into the Inconel 600 reactor having an internal diameter of 20.6 mm Φ and a length of 500 mm (electric heater heating method: passivated at a temperature of 500 ° C. with fluorine gas) at a total flow rate of 30 NL / hr from two gas inlets. The internal temperature of the reactor was maintained at 420 ° C. Next, the mixed gas containing hydrogen fluoride was flowed through the two gas inlets at a flow rate of 50 NL / hr in total, and the low boiling point component was removed from one of the gas inlets. Was flowed at a flow rate of 3.5 NL / hr. From the other gas inlet, fluorine gas was introduced at a flow rate of 3.85 NL / hr for reaction. After 3 hours, the outlet gas of the reactor was contacted with aqueous potassium hydroxide solution and aqueous potassium iodide solution to remove hydrogen fluoride and unreacted fluorine gas. After drying by contacting with a dehydrating agent, the dried gas composition was analyzed by gas chromatography. The analysis results are shown in Table 10 below.

The dry gas containing hexafluoroethane as a main component was cooled, collected, and distilled to purify it. The purified gas was analyzed by gas chromatography using TCD, FID, ECD and GC-MS to obtain the results shown in Table 11 below.

As the analysis results in Table 11 clearly show, hexafluoroethane contains virtually no other impurities, thus showing that high purity hexafluoroethane with a purity of 99.9997 vol% or more can be obtained.

Example 4

The reaction [Step (1)] was carried out under the same conditions and operation as in Example 3, except that 100 ml of the catalyst (Catalyst Example 3) was filled and the mixed gas of Starting Material Example 4 was used. The reactor outlet gas was treated in the same way and then analyzed to obtain the results shown in Table 12 below.

After mixing the gas mixture containing pentafluoroethane of the composition shown in Table 12 by the above-mentioned manufacturing method as a main component by a well-known method, and removing low boiling point components, such as an inert gas and hydrogen gas, Direct fluorination reaction [step (2)] was performed with fluorine gas using the same conditions and operation. According to the same method as in Example 3, the gas obtained by treating the reactor outlet gas was analyzed by gas chromatography to obtain the results shown in Table 13 below.

The mixed gas containing hexafluoroethane as a main component was cooled and collected, and then purified by distillation. By analyzing the purified gas, it can be confirmed that the purity of hexafluoroethane is 99.9998 vol% or more, the content of chlorine compound contained as impurities is less than 1 volppm, and the content of pentafluoroethane, the starting material, is less than 1 volppm. there was.

Comparative Example 1

The reaction [Step (1)] was carried out under the same conditions and operation as in Example 3 except that the reaction temperature was 430 ° C., and the product was analyzed. The results are shown in Table 14 below.

As the analytical result of Table 14 clearly shows, when the step (1) is carried out at a reaction temperature higher than 400 ° C, since the excess hydrogenation reaction proceeds, the amount of 1,1,1-trifluoroethane produced Increased significantly. In addition, methane and ethane were produced and catalyst deterioration was observed.

Comparative Example 2

Except that reaction temperature was 130 degreeC, reaction [process (1)] was performed by the same conditions and operation as Example 3, and the product was analyzed. When the step (1) was carried out at a temperature lower than 150 ° C, the hydrogenation reaction of the chlorine compound was almost completely inhibited, and as a result, the conversion rate of chloropentafluoroethane was about 19%.

Comparative Example 3

The fluorination reaction [step (2)] was carried out directly under the same conditions and operation as in Example 3, except that the mixed gas of the starting raw material example 3 was used, and then the inert gas and hydrogen gas contained in the reactor outlet gas were removed. And gas chromatography. The results are shown in Table 15 below.

As Table 15 clearly shows, chlorotrifluoromethane which was difficult to separate was produced by direct fluorination reaction using pentafluoroethane containing a chlorine compound at a high concentration.

According to the production method of the present invention, it is possible to obtain high purity CF ₃ CF ₃ , which CF ₃ CF ₃ is suitable for use as an etching gas or a cleaning gas in a semiconductor device manufacturing process.

Claims (34)

Hexafluoroethane comprising the step of fluorinating the chlorotrifluoromethane by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane at 200 to 450 ° C. with gaseous hydrogen fluoride in the presence of a fluorination catalyst. Method of preparation. The production method according to claim 1, wherein the fluorination catalyst is a supported catalyst or bulk catalyst mainly composed of trivalent chromium oxide. The process according to claim 1 or 2, wherein the molar ratio of hydrogen fluoride and mixed gas (mixed gas containing hydrogen fluoride / hexafluoroethane and chlorotrifluoromethane) is in the range of 0.05 to 10. The production method according to claim 1 or 2, wherein the concentration of chlorotrifluoromethane contained in the mixed gas is 0.1 vol% or less. The process according to claim 1 or 2, wherein the mixed gas is obtained by reacting dichlorotetrafluoroethane and / or chloropentafluoroethane with gaseous hydrogen fluoride in the presence of a fluorination catalyst. The method according to claim 1 or 2, wherein the mixed gas is obtained by reacting tetrafluoroethane and / or pentafluoroethane with fluorine gas. (1) fluorinated chlorotrifluoromethane by reacting a mixed gas containing hexafluoroethane and chlorotrifluoromethane at 200 to 450 ° C. with gaseous hydrogen fluoride in the presence of a fluorination catalyst, followed by tetrafluoro Converting it into methane, (2) A method for producing hexafluoroethane comprising distilling a mixed gas containing tetrafluoromethane and hexafluoroethane obtained in step (1) to obtain purified hexafluoroethane. The production method according to claim 7, wherein the fluorination catalyst of step (1) is a supported catalyst or a bulk catalyst mainly composed of trivalent chromium oxide. The molar ratio of hydrogen fluoride and mixed gas (mixed gas containing hydrogen fluoride / hexafluoroethane and chlorotrifluoromethane) in the step (1) is in the range of 0.05 to 10. Phosphorus manufacturing method. The production method according to claim 7 or 8, wherein the concentration of chlorotrifluoromethane contained in the mixed gas of step (1) is 0.1 vol% or less. The process according to claim 7 or 8, wherein the mixed gas of step (1) is obtained by reacting dichlorotetrafluoroethane and / or chloropentafluoroethane with gaseous hydrogen fluoride in the presence of a fluorination catalyst. The production method according to claim 7 or 8, wherein the mixed gas of step (1) is obtained by reacting tetrafluoroethane and / or pentafluoroethane with fluorine gas.  (1) hydrogenating the chlorine compound by reacting pentafluoroethane containing a chlorine compound having 1 to 3 carbon atoms at 150 to 400 ° C with hydrogen in the gas phase in the presence of a hydrogenation catalyst; (2) A method for producing hexafluoroethane comprising the step of reacting the product of step (1) with fluorine in the gas phase in the presence of diluent gas to produce hexafluoroethane. The production process according to claim 13, wherein the product of step (1) used in step (2) is purified pentafluoroethane obtained by distilling the crude product of step (1). The production method according to claim 13 or 14, further comprising a step of distilling the product obtained in step (2) to purify hexafluoroethane. The process according to claim 13 or 14, further comprising the step of removing hydrochloric acid from the reaction product obtained in step (1). 15. The method of claim 13 or 14, wherein the chlorine compound is chloromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and chlorotrifluoro It is at least one compound selected from the group consisting of roethylene. The production method according to claim 13 or 14, wherein the amount of the chlorine compound contained in the pentafluoroethane containing the chlorine compound used in the step (1) is 1 vol% or less. 19. The process according to claim 18, wherein the amount of chlorine compound contained in pentafluoroethane containing chlorine compound used in step (1) is 0.5 vol% or less. The production method according to claim 13 or 14, wherein the hydrogenation catalyst of step (1) contains at least one element selected from platinum group metals. The process according to claim 20, wherein the hydrogenation catalyst of step (1) contains at least one element selected from platinum group metals supported on at least one carrier selected from the group consisting of activated carbon, alumina and fluorinated alumina. The production method according to claim 13 or 14, wherein the amount of hydrogen used in step (1) is 1 to 20 in molar ratio with respect to pentafluoroethane containing a chlorine compound. The production method according to claim 13 or 14, wherein the amount of trifluoroethane contained in the product of step (1) used in step (2) is 0.2 vol% or less. The production method according to claim 13 or 14, wherein the amount of the chlorine compound having 1 to 3 carbon atoms contained in the product of step (1) used in step (2) is 0.05 vol% or less. The production method according to claim 13 or 14, wherein the dilution gas of step (2) contains at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, and hydrogen fluoride. The production method according to claim 25, wherein the dilution gas of step (2) is a gas rich in hydrogen fluoride. The production method according to claim 13 or 14, wherein the reaction temperature of the step (2) is 250 to 500 ° C. The production method according to claim 27, wherein the reaction temperature of the step (2) is 350 to 450 ° C. 15. The pentafluoroethane containing chlorine compound used in the step (1) is a gas mainly containing pentafluoroethane obtained by reacting tetrachloroethylene or its fluoride with hydrogen fluoride. Manufacturing method. The production method according to claim 29, wherein the gas containing pentafluoroethane as a main component is a gas obtained by distilling a gas obtained by reacting tetrachloroethylene or a fluoride thereof with hydrogen fluoride. delete delete delete delete