KR100580915B1 - Process for Purifying Pentafluoroethane, Process for Producing the Same, and Use Thereof - Google Patents

Abstract

Crude pentafluoroethane containing at least one compound selected from the group consisting of hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom, and hydrochlorocarbons containing one carbon atom And an adsorbent comprising a zeolite having an average pore size of 3 to 6 mm 3 and a silica / aluminum ratio of 2.0 or less and / or a carbonaceous adsorbent having an average pore size of 3.5 to 6 mm 3 to reduce the content of the compound. How to include. As the low temperature refrigerant or the etching gas, the purified gas may be used.

Description

Process for Purifying Pentafluoroethane, Process for Producing the Same, and Use Thereof}

This application claims the benefit of the filing date of U.S. Provisional Application 60 / 394,267, filed on July 9, 2002 under 35 U.S.C 111 (b), pursuant to 35 U.S.C §119 (e) (1). An application filed under § 111 (a).

The present invention relates to a process for the purification, preparation and use of pentafluoroethane.

Pentafluoroethane (CF ₃ CHF ₂ ) is used, for example, as a low temperature refrigerant or etching gas, and also as a raw material for the preparation of hexafluoroethane (CF ₃ CF ₃ ).

For the preparation of pentafluoroethane, for example,

(1) a method of fluorination of tetrachloroethylene (CCl ₂ = CCl ₂ ) or its fluoride with hydrogen fluoride (see Japanese Patent Application Laid-Open No. 8-268932),

(2) a method of reducing and hydrogenating chloropentafluoroethane (CF ₃ CClF ₂ ) (see Japanese Patent No. 2540409), and

(3) Methods such as a method of reacting halogen-containing ethylene with fluorine gas (see Japanese Patent Application Laid-Open No. Hei 1-38034) have been known in the past.

Pentafluoroethane produced by these methods contains various impurities such as hydrochlorocarbon (HCC), chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC).

In order to obtain high purity pentafluoroethane, the impurities must be removed as much as possible. Among these impurities, various purification methods have been proposed to remove chlorofluorocarbons in order to achieve high purity as well as to prevent destruction of the ozone layer. Since chloropentafluoroethane has a boiling point close to that of pentafluoroethane, it is a compound that is difficult to be separated by general distillation, but instead the following purification method can be used.

(1) Method by extractive distillation (see Japanese Patent Application Laid-Open No. 9-508626)

(2) A method of reducing and hydrogenating chloropentafluoroethane (see Japanese Patent Application Laid-Open No. Hei 8-301801).

(3) A method of removing chloropentafluoroethane after fluorination with hydrogen fluoride (see Japanese Patent Laid-Open No. 2001-48816).

(4) Method of removing chloropentafluoroethane after adsorbing using an adsorbent and then removing it (see Japanese Patent Application Laid-Open No. Hei 6-92879).

Chloromethane (CH ₃ Cl), one of the hydrochlorocarbons, forms an azeotrope or an azeotrope-like mixture with pentafluoroethane, making the compound very difficult to separate from pentafluoroethane. Hydrofluorocarbons, difluoromethane (CH ₂ F ₂ ) and 1,1,1-trifluoroethane (CF ₃ CF ₃ ), respectively, form an azeotropic or azeotropic mixture with pentafluoroethane. This makes it very difficult to separate these compounds from pentafluoroethane.

Hydrochlorocarbons or hydrofluorocarbons, which are difficult to separate, and a method of purifying and removing impurities including them, for example, a purification method by extractive distillation, and a purification method of removing the impurities by adsorption using activated carbon, Known. However, since the purification method by extractive distillation requires a number of expensive facilities such as a distillation column, the apparatus cost is very high. In addition, the purification method by adsorption using activated carbon cannot provide a sufficient effect.

Under these circumstances, it is an object of the present invention to provide an industrially advantageous purification method for obtaining high purity pentafluoroethane that can be used as a low temperature refrigerant or etching gas. It is another object of the present invention to provide a method and use of the pentafluoroethane.

In order to solve the above problems, the inventors of the present invention have found that, as a result of intensive research, hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom, and hydrochlorocarbons containing one carbon atom Crude pentafluoroethane containing at least one compound selected from the group consisting of zeolites having an average pore size of 3 to 6 ms and a silica / aluminum ratio of 2.0 or less and / or carbon having an average pore size of 3.5 to 6 ms It has been found that the object of the present invention is achieved by using a process of reducing the content of a compound contained as an impurity in crude pentafluoroethane by contacting with an adsorbent comprising a vaginal adsorbent. The present invention has been accomplished based on this finding. The present invention provides a method for purifying pentafluoroethane, a production method, and a use thereof according to the following [1] to [13].

[One]. Crude pentafluoro containing at least one compound selected from the group consisting of hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom, and hydrochlorocarbons containing one carbon atom The ethane is contacted with an adsorbent comprising a zeolite having an average pore size of 3 to 6 GPa and a silica / aluminum ratio of 2.0 or less and / or a carbonaceous adsorbent having an average pore size of 3.5 to 6 GPa and impurity in crude pentafluoroethane. Method for purifying pentafluoroethane, characterized in that it comprises a step of reducing the content of the compound contained as.

[2]. The method for purifying pentafluoroethane according to [1], wherein the hydrofluorocarbons containing one carbon atom are selected from the group consisting of fluoromethane, difluoromethane and trifluoromethane.

[3]. The method for purifying pentafluoroethane according to [1], wherein the hydrochlorofluorocarbons containing one carbon atom are chlorodifluoromethane.

[4]. The method for purifying pentafluoroethane according to [1], wherein the hydrochlorocarbons containing one carbon atom are selected from the group consisting of chloromethane, dichloromethane and trichloromethane.

[5]. The method for purifying pentafluoroethane according to any one of [1] to [4], wherein the total content of the compound contained as an impurity in the crude pentafluoroethane is 1% by volume or less.

[6]. The method for purifying pentafluoroethane according to any one of [1] to [5], wherein the crude pentafluoroethane is brought into contact with the adsorbent under a pressure of 1 MPa or less.

[7]. The method for purifying pentafluoroethane according to any one of [1] to [6], wherein the total content of the compound contained as an impurity in the crude pentafluoroethane is reduced to 150 vol ppm or less.

[8]. Pentafluor according to any one of [1] to [7], wherein the total content of hydrofluorocarbons containing one carbon atom contained as an impurity in crude pentafluoroethane is reduced to 100 vol ppm or less. Purification method of roethane.

[9]. Pentafluor according to any one of [1] to [8], wherein the total content of hydrochlorocarbons containing one carbon atom contained as an impurity in crude pentafluoroethane is reduced to 50 vol ppm or less. Purification method of roethane.

[10]. The crude pentaplefuoroethane according to any one of [1] to [9],

(1) fluorinated at least one member selected from the group consisting of tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting with hydrogen fluoride in the presence of a catalyst to obtain pentafluoroethane; And

(2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) A method for purifying pentafluoroethane, which is obtained by a method comprising contacting pentafluoroethane with hydrogen and then contacting oxygen and / or an oxygen-containing compound.

[11]. (1) fluorinated at least one member selected from the group consisting of tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting with hydrogen fluoride in the presence of a catalyst to obtain pentafluoroethane;

(2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) Contacting pentafluoroethane with hydrogen, followed by contact with oxygen and / or an oxygen containing compound; And

(3) A process for producing pentafluoroethane comprising the step of purifying the pentafluoroethane obtained in the step (2) using the method according to any one of the above [1] to [10].

[12]. A method for producing hexafluoroethane comprising the step of reacting purified pentafluoroethane with fluorine gas using the method according to any one of [1] to [10].

[13]. A refrigerant comprising pentafluoethane refined using the method according to any one of [1] to [10].

The preferred embodiment of the present invention is described below.

As described above, for the production of pentafluoroethane, for example, a method is known in which tetrachloroethylene or its fluoride is fluorinated with hydrogen fluoride (HF) in the presence of a fluorination catalyst.

When pentafluoroethane is produced by the above method, impurities, which are difficult to be separated from pentafluoroethane, are contained in the material even when a generally used purification process such as distillation is performed. Examples of such impurities include hydrofluorocarbons, hydrochlorofluorocarbons and hydrochlorocarbons. Moreover, even if the method of hydrogen-reducing chloropentafluoroethane in presence of a catalyst is used, these impurities are contained similarly. Therefore, in order to purify pentafluoroethane with high purity, these impurities must be removed.

The method for purifying pentafluoroethane of the present invention is selected from the group consisting of hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom, and hydrochlorocarbons containing one carbon atom. Adsorbents comprising crude pentafluoroethane containing at least one compound comprising a zeolite having an average pore size of 3 to 6 GPa and a silica / aluminum ratio of 2.0 or less and / or a carbonaceous adsorbent having an average pore size of 3.5 to 6 GPa It is characterized by reducing the content of the compound contained as an impurity in the crude pentafluoroethane.                 

The hydrofluorocarbon containing one carbon atom contained as an impurity in crude pentafluoroethane may be at least one compound selected from the group consisting of fluoromethane, difluoromethane and trifluoromethane. Hydrochlorofluorocarbons containing one carbon atom may be chlorodifluoromethane. The hydrochlorocarbon containing one carbon atom may be at least one compound selected from the group consisting of chloromethane, dichloromethane and trichloromethane. Crude pentafluoroethane containing these impurities is difficult to purify only by distillation operation.

The present inventors conducted the study by changing the type of the adsorbent or the adsorption conditions, while taking into account the pore size and polarity of the adsorbent.

As a result, the impurities described above can be selectively adsorbed and removed by contacting a zeolite having an average pore size of 3 to 6 GPa and a silica / aluminum ratio (Si / Al ratio) of 2.0 or less. Even if the silica / aluminum ratio is 2.0 or less, when the average pore size of the zeolite is less than 3 GPa or more than 6 GPa, the effect of reducing the impurities is not obtained. Further, even when the average pore size is in the range of 3 to 6 mm 3, when the silica / aluminum ratio of the zeolite exceeds 2.0, the effect of reducing the amount of the impurity is not obtained.

It has also been found that the impurity can be selectively adsorbed and removed by contacting the impurity with a carbonaceous adsorbent (molecular sieve carbon) having an average pore size of 3.5 to 6 kPa. When the average pore size of the carbonaceous adsorbent used is less than 3.5 mm 3 or more than 6 mm 3, the effect of reducing the impurities is not obtained. For example, activated carbon having an average pore size of about 35 mm 3 is generally used and is known to have a strong adsorption force, but this cannot provide the effect of reducing impurities.

The zeolite and the carbonaceous adsorbent may be used alone or in combination of any two of them.

As for the total content of these impurities contained as an impurity in crude pentafluoroethane, 1 volume% or less is preferable, and 0.5 volume% or less is more preferable. If the total content of impurities exceeds 1% by volume, the amount of adsorbent used is increased, or the equipment cost is unreasonably increased.

In the method for purifying pentafluoroethane of the present invention, the method of bringing crude pentafluoroethane containing these impurities into contact with an adsorbent is not particularly limited, and for example, these are contacted by either a gas phase or a liquid phase. You can. The method of bringing them into contact with the liquid phase is preferable because it is efficient. For contacting in the liquid phase, known methods such as batch systems or continuous systems can be used. For example, two units of a fixed bed adsorption tower are installed, and when one adsorption tower reaches saturated adsorption, it is possible to use a method in which regeneration is performed by switching to another unit. The pressure for bringing the crude pentafluoroethane into contact with the adsorbent is preferably 1 MPa or less. If the pressure exceeds 1 MPa, the apparatus cost is unreasonably increased.

Crude pentafluoroethane is a group consisting of (1) tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting at least one member selected from hydrogen fluoride in the presence of a fluorination catalyst to obtain pentafluoroethane;

(2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) It is preferable that the pentafluoroethane is obtained by a method comprising contacting hydrogen with hydrogen and then contacting oxygen and / or an oxygen-containing compound.

In the step (1), a method of obtaining pentafluoroethane by performing a fluorination reaction in two steps with hydrogen fluoride in the presence of a raw material such as tetrachloroethylene and a fluorination catalyst is used. The fluorination catalyst is preferably a supported catalyst or bulk catalyst containing trivalent chromium oxide as a main component.

In the step (2), when performing the step of contacting the pentafluoroethane obtained in the step (1) with hydrogen, at least one member selected from the group consisting of palladium, rhodium, ruthenium, rhenium, platinum and gold is supported. It may be carried out in the presence of a supported catalyst supported on the bed. Reaction temperature is 150-400 degreeC. By contact with hydrogen, for example, reduction and hydrogenation reactions such as hydrochlorocarbons occur.

In the step (2), when performing the step of contacting the pentafluoroethane obtained in the step (1) with oxygen and / or an oxygen-containing compound, this is the presence of a supported catalyst or bulk catalyst mainly composed of trivalent chromium oxide. Or at least one selected from palladium, rhodium, ruthenium, rhenium, platinum and gold may be carried out in the presence of a supported catalyst supported on a support. Reaction temperature is 150-400 degreeC. Examples of oxygen-containing compounds that can be used include nitrogen monoxide (NO), nitrous oxide (N ₂ O), nitrogen dioxide (NO ₂ ), and ozone (O ₃ ). By this treatment, hydrofluorocarbons contained as impurities can be converted into CO ₂ or the like. Step (2) is preferably carried out by bringing the pentafluoroethane obtained in step (1) into contact with hydrogen, followed by contact with oxygen and / or an oxygen containing compound.

After treating the compound contained as an impurity in the crude pentafluoroethane with an adsorbent, the total content of the compound contained in the pentafluoroethane can be reduced to 150 volppm or less, and can be reduced to 100 volppm or less. Further, by using the purification method of the present invention, the total content of hydrofluorocarbons containing one carbon atom contained as impurities in the purified pentafluoroethane can be reduced to 100 volppm or less, and to 50 volppm or less. It can also be reduced. Further, the total content of hydrochlorocarbons containing one carbon atom can be reduced to 50 vol ppm or less, and can also be reduced to 30 vol ppm or less. The content of the compound contained as an impurity in pentafluoroethane can be measured by gas chromatography (GC) or gas chromatography mass spectrometry (GC-MS) using the TCD method or the FID method.

In addition, the present invention is from the group consisting of (1) tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting at least one selected with hydrogen fluoride in the presence of a fluorination catalyst to obtain pentafluoroethane,                 

(2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) Contacting pentafluoroethane with hydrogen followed by contact with oxygen and / or an oxygen containing compound, and

(3) It provides a method for producing pentafluoroethane comprising the step of purifying the pentafluoroethane obtained in step (2) using the above process.

The use of pentafluoroethane obtained using the purification process of the present invention is described below.

High purity pentafluoroethane replaces chlorodifluoromethane (CHClF ₂ ) commonly used as the working fluid of cryogenic refrigerants, which is difluoromethane / pentafluoroethane / 1,1,1,2-tetrafluoro It can be used as a mixed refrigerant containing ethane, and can also be used as a mixed refrigerant containing difluoromethane / pentafluoroethane.

In addition, high purity pentafluoroethane can be used as a raw material for the production of hexafluoroethane. In particular, in the method for producing hexafluoroethane by the reaction of pentafluoroethane and fluorine gas, when a high-purity pentafluoroethane is used as a raw material, generation of impurities that are difficult to separate from the target hexafluoroethane is prevented. can do. In addition, in the case of using high-purity pentafluoroethane as a raw material, in setting the fluorination reaction conditions, the range can be widened, and as a result, the reaction can be stably controlled and the purification process can be simplified.                 

High-purity pentafluoroethane or a mixed gas thereof, an inert gas (He, N ₂ , Ar, etc.), HCl, O ₂ , H _2, or the like can be used as the etching gas in the etching step of the semiconductor device fabrication method. In the fabrication method of semiconductor devices such as LSI, TFT, and organic EL, the thin film or the thick film is formed using a CVD method, a sputtering method, or a vapor deposition method, and a circuit pattern can be formed by etching. As the gas containing pentafluoroethane can be used. Etching using pentafluoroethane can be performed under various dry etching conditions such as plasma etching and microwave etching.

The present invention is described in more detail by the following examples, but the present invention is not limited to these examples.

Preparation Example 1 of Crude Pentafluoroethane

(Raw material example 1)

Tetrachloroethylene and hydrogen fluoride were introduced into the first reactor filled with a catalyst to obtain intermediates 2,2-dichloro-1,1,1-trifluoroethane and chloro-1,1,1,2-tetrafluoroethane. The gas containing as a main component was manufactured. The gas was introduced with HF into a second reactor to produce pentafluoroethane. The pentafluoroethane prepared was distilled to pentafluoropentane containing chloropentafluoroethane, fluoromethane, difluoromethane, chloromethane, chlorodifluoromethane, 1,1,1-trifluoromethane and the like as impurities. Fluoroethane was obtained. The purity of pentafluoroethane was about 99.4% by volume. The pentafluoroethane was then reacted with hydrogen in the presence of a conventional hydrogenation catalyst (reaction pressure: 0.15 MPa, reaction temperature: 220 ° C.). The acid content contained in the product containing pentafluoroethane as a main component was removed by a known method, and the residue was distilled off to obtain crude pentafluoroethane. The crude pentafluoroethane obtained was analyzed by gas chromatography and found to have the composition shown in Table 1.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.8404 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0024 CF ₃ CH ₃ 0.0879 CH ₂ F ₂ 0.0482 CHF ₃ 0.0021 CHClF ₂ 0.0020 CH ₃ Cl 0.0088

Preparation Example 2 of Crude Pentafluoroethane

(Raw material example 2)

Pentafluoroethane obtained in Raw Material Example 1 was introduced together with air into a reactor filled with a palladium / aluminum catalyst, and reacted under the conditions such that the reaction pressure was 0.2 MPa and the reaction temperature was 280 ° C. Carbon dioxide and acid content contained in the outlet gas of the reactor were partially removed by washing the gas with an aqueous potassium hydroxide solution, and then the gas was distilled off to obtain crude pentafluoroethane. The obtained jofentafluoroethane was analyzed by gas chromatography and found to have the composition shown in Table 2.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.9522 CF ₃ CClF ₂ 0.0081 CF ₃ CH ₂ F 0.0018 CF ₃ CH ₃ 0.0088 CH ₂ F ₂ 0.0246 CHF ₃ 0.0019 CHClF ₂ 0.0020 CH ₃ Cl 0.0087

Preparation Example 3 of Crude Pentafluoroethane

(Raw material example 3)

To the crude pentafluoroethane obtained in Raw Material Example 2, CH ₂ F ₂ and CH ₃ Cl were further added to prepare crude pentafluoroethane Raw Material 3. This was analyzed by gas chromatography and found to have the composition shown in Table 3.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.6322 CF ₃ CClF ₂ 0.0081 CF ₃ CH ₂ F 0.0018 CF ₃ CH ₃ 0.0087 CH ₂ F ₂ 0.2325 CHF ₃ 0.0019 CHClF ₂ 0.0020 CH ₃ Cl 0.1128

Example 1

Zeolite (molecular sieve 4A (manufactured by Union Showa K.K., average pore size: 3.5 GPa, silica / aluminum ratio = 1.0)) (20 g) was filled in a cylinder made of 200 ml stainless steel, and vacuum dried. While cooling the said cylinder, about 100 g of crude pentafluoroethane of the raw material example 1 was filled here, and it stirred intermittently, maintaining the temperature at -10 degreeC. After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 4 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.8979 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0021 CF ₃ CH ₃ 0.0880 CH ₂ F ₂ 0.0001 CHF ₃ 0.0015 CHClF ₂ 0.0019 CH ₃ Cl 0.0003

As is apparent from the analysis results shown in Table 4, CH ₂ F ₂ and CH ₃ Cl could be selectively adsorbed and removed.

Example 2

In the same manner as in Example 1, molecular sieve 4A (20 g) was placed in a 200 ml stainless cylinder and vacuum dried. While cooling the cylinder, about 100 g of crude pentafluoroethane of Raw Material Example 2 was filled therein, and the mixture was stirred intermittently while maintaining the temperature at room temperature (20 ° C). After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 5 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.9790 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0017 CF ₃ CH ₃ 0.0087 CH ₂ F ₂ 0.0001 CHF ₃ 0.0009 CHClF ₂ 0.0012 CH ₃ Cl 0.0002

As is clear from the analytical results shown in Table 5, high purity pentafluoroethane having a purity of 99.97% by volume or more was obtained.

Example 3

In the same manner as in Example 1, molecular sieve 4A (30 g) was charged to a 200 ml stainless cylinder. While cooling the cylinder, about 100 g of crude pentafluoroethane of the raw material example 3 was filled therein and dried in vacuo, and then the mixture was stirred intermittently while maintaining the temperature at room temperature (25 ° C). After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 6 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.9789 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0016 CF ₃ CH ₃ 0.0087 CH ₂ F ₂ 0.0011 CHF ₃ 0.0006 CHClF ₂ 0.0008 CH ₃ Cl 0.0001

Example 4                 

A carbonaceous adsorbent (molecular sieve carbon manufactured by Takeda Chemical Industries, Ltd., average pore size: 4 mm 3) (20 g) was charged into a 200 ml stainless cylinder, and vacuum dried. While cooling the cylinder, about 100 g of crude pentafluoroethane of Raw Material Example 1 was filled, and the mixture was stirred intermittently while maintaining the temperature at -20 ° C. After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 7 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.8992 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0023 CF ₃ CH ₃ 0.0880 CH ₂ F ₂ 0.0003 CHF ₃ 0.0006 CHClF ₂ 0.0012 CH ₃ Cl 0.0002

As is apparent from the analytical results shown in Table 7, CH ₂ F ₂ and CH ₃ Cl can be selectively adsorbed and removed.

Example 5

Molecular sieve 4A (15 g) used in Example 1 and 15 g of molecular sieve carbon used in Example 4 were mixed, filled into a 200 ml stainless cylinder, and vacuum dried. While cooling the cylinder, about 100 g of crude pentafluoroethane of Raw Material Example 3 was filled therein, and the mixture was stirred intermittently while maintaining the temperature at room temperature (25 ° C). After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 8 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.9786 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0017 CF ₃ CH ₃ 0.0088 CH ₂ F ₂ 0.0004 CHF ₃ 0.0007 CHClF ₂ 0.0013 CH ₃ Cl 0.0003

Comparative Example 1

Zeolite (molecular sieve 13X (manufactured by Union Showa K.K., average pore size: 10 μs, silica / aluminum ratio = 1.2)) (20 g) was charged to a 200 ml stainless cylinder and vacuum dried. While cooling the said cylinder, about 100 g of crude pentafluoroethane of the raw material example 2 was filled here, and it stirred intermittently, maintaining the temperature at room temperature (25 degreeC). After about 20 hours, the liquid phase was analyzed by gas chromatography. Table 9 shows the analysis results.

compound Concentration (% by volume) CF ₃ CHF ₂ 99.9452 CF ₃ CClF ₂ 0.0082 CF ₃ CH ₂ F 0.0002 CF ₃ CH ₃ 0.0090 CH ₂ F ₂ 0.0251 CHF ₃ 0.0012 CHClF ₂ 0.0021 CH ₃ Cl 0.0090

As apparent from the analysis results shown in Table 9, even if the silica / aluminum ratio was 2.0 or less, when the average pore size exceeded 6 mm 3, selective adsorption and removal could not be obtained.

Comparative Example 2                 

Activated carbon (granular Shirosagi KL (manufactured by Takeda Chemical Industries, Ltd., average pore size: 35 mm 3)) (20 g) was charged to a 200 ml stainless cylinder, and vacuum dried. While cooling the said cylinder, about 100 g of crude pentafluoroethane of the raw material example 2 was filled here, and it stirred intermittently, maintaining the temperature at room temperature (25 degreeC). After about 20 hours, the liquid phase was analyzed by gas chromatography. As in Comparative Example 1, selective adsorption and removal could not be obtained, and a reduction in the content of CH ₂ F ₂ or CH ₃ Cl could not be obtained.

Comparative Example 3

Purification was carried out under the same conditions as in Comparative Example 1, except that a 200 ml stainless cylinder was filled with zeolite (H-ZSM-5 (manufactured by NE Chemcat Corporation, average pore size: 6 μs, silica / aluminum ratio = 15)). Was performed. As a result of the analysis, no reduction of the CH ₂ F ₂ or CH ₃ Cl content was confirmed.

As described above, when the purification method of the present invention is used, high purity pentafluoroethane can be obtained. The pentafluoroethanes obtained according to the invention can be used as raw materials for the preparation of low temperature refrigerants or high purity hexafluoroethanes.

Claims (13)

Crude pentafluoro containing at least one compound selected from the group consisting of hydrofluorocarbons containing one carbon atom, hydrochlorofluorocarbons containing one carbon atom, and hydrochlorocarbons containing one carbon atom The ethane is contacted with an adsorbent comprising a zeolite having an average pore size of 3 to 6 GPa and a silica / aluminum ratio of 2.0 or less and / or a carbonaceous adsorbent having an average pore size of 3.5 to 6 GPa and impurity in crude pentafluoroethane. Method for purifying pentafluoroethane, characterized in that it comprises a step of reducing the content of the compound contained as. The method for purifying pentafluoroethane according to claim 1, wherein the hydrofluorocarbons containing one carbon atom are selected from the group consisting of fluoromethane, difluoromethane and trifluoromethane. The method for purifying pentafluoroethane according to claim 1, wherein the hydrochlorofluorocarbons containing one carbon atom are chlorodifluoromethane. The method for purifying pentafluoroethane according to claim 1, wherein the hydrochlorocarbons containing one carbon atom are selected from the group consisting of chloromethane, dichloromethane and trichloromethane. The method for purifying pentafluoroethane according to any one of claims 1 to 4, wherein the total content of the compound contained as impurities in the crude pentafluoroethane is 1% by volume or less. The method for purifying pentafluoroethane according to any one of claims 1 to 4, wherein crude pentafluoroethane is brought into contact with the adsorbent under a pressure of 1 MPa or less. The method for purifying pentafluoroethane according to any one of claims 1 to 4, wherein the total content of the compound contained as impurities in the crude pentafluoroethane is reduced to 150 vol ppm or less. The penta according to any one of claims 1 to 4, wherein the total content of hydrofluorocarbons containing one carbon atom contained as an impurity in crude pentafluoroethane is reduced to 100 vol ppm or less. Method for Purifying Fluoroethane. The total content of hydrochlorocarbons containing one carbon atom contained as an impurity in crude pentafluoroethane is reduced to 50 parts by ppm or less. Method for Purifying Pentafluoroethane. The crude pentafluoroethane according to any one of claims 1 to 4, wherein (1) fluorinated at least one member selected from the group consisting of tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting with hydrogen fluoride in the presence of a catalyst to obtain pentafluoroethane; And (2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) A method for purifying pentafluoroethane, which is obtained by a method comprising contacting pentafluoroethane with hydrogen and then contacting oxygen and / or an oxygen-containing compound. (1) fluorinated at least one member selected from the group consisting of tetrachloroethylene, 2,2-dichloro-1,1,1-trifluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane Reacting with hydrogen fluoride in the presence of a catalyst to obtain pentafluoroethane; (2) contacting pentafluoroethane obtained in step (1) with hydrogen; contacting pentafluoroethane obtained in step (1) with oxygen and / or an oxygen-containing compound, or obtained in step (1) Contacting pentafluoroethane with hydrogen, followed by contact with oxygen and / or an oxygen containing compound; And (3) A process for producing pentafluoroethane comprising the step of purifying the pentafluoroethane obtained in the step (2) using the method according to any one of claims 1 to 4. A method for producing hexafluoroethane comprising the step of reacting purified pentafluoroethane with fluorine gas using the method according to any one of claims 1 to 4. delete