JP2003055277A - Method for producing hexafluoroethane and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a method for industrially and advantageously producing a high-purity hexafluorothane usable as an etching gas or a cleaning gas and the use thereof. SOLUTION: This method for producing the hexafluoroethane comprises (1) a step of reacting pentafluoroethane containing a chlorine-containing compound having 1-3 carbon atoms with hydrogen in the presence of a hydrogenating catalyst in the vapor phase at 150-400 deg.C and hydrogenating the chlorine- containing compound and (2) reacting the resultant product in the step (1) with fluorine in the presence of a diluting gas in the vapor phase and producing the hexafluoroethane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing hexafluoroethane and its use.

[0002]

_2. Description of the Related Art Pentafluoroethane (CF ₃ CHF ₂ )
Is used, for example, as a low-temperature refrigerant or as a raw material for producing hexafluoroethane (CF ₃ CF ₃ ). The following methods have been conventionally known as methods for producing pentafluoroethane.

For example, (1) perchlorethylene (CC
l ₂ = CCl ₂ ) or a method of fluorinating a fluorinated product thereof with hydrogen fluoride (JP-A-8-268932 and JP-A-9-511515), (2) chloropentafluoroethane (CClF ₂ CF ₃ ). (Japanese Patent No. 2540409), and (3) a method of reacting halogen-containing ethylene with fluorine gas (Japanese Patent Laid-Open No. 1-33).
No. 8034), and the like.

When these methods for producing pentafluoroethane are used, the objective pentafluoroethane contains a chlorine-containing compound containing a chlorine atom in the molecule as a main impurity. Examples of the chlorine-containing compound include compounds containing one carbon atom, such as chloromethane, chlorodifluoromethane, chlorotrifluoromethane, compounds containing two carbon atoms, chloropentafluoroethane, dichlorotetrafluoroethane, and chloro. Examples thereof include tetrafluoroethane, chlorotrifluoroethane, and unsaturated compounds such as chlorotrifluoroethylene.

When hexafluoroethane is produced by a direct fluorination reaction in which pentafluoroethane and fluorine gas (F ₂ ) are reacted, when pentafluoroethane contains the above-mentioned chlorine-containing compound, it becomes fluorine gas. The reaction of produces chlorine, hydrogen chloride, chlorine fluoride, or different kinds of chlorofluorocarbons. Perfluorocarbon (PFC) in pentafluoroethane
No particular problem occurs even if the compounds are contained, but for example, chloromethane (CH ₃ Cl) or chlorodifluoromethane (CH
ClF ₂ ) reacts with fluorine gas to produce chlorotrifluoromethane (CClF ₃ ). Since hexafluoroethane and chlorotrifluoromethane form an azeotropic mixture, removal of chlorotrifluoromethane is difficult even if distillation or adsorption purification is performed. Therefore, when hexafluoroethane is produced by reacting pentafluoroethane with fluorine gas, it is desirable to use pentafluoroethane containing as little chlorine-containing compound as possible.

According to the conventional method for producing pentafluoroethane, the chlorine-containing compound contained in pentafluoroethane may be contained in a total amount of about 1 vol% in many cases. Therefore, it is conceivable to remove these chlorine-containing compounds contained in pentafluoroethane and repeat the distillation operation in order to increase the purity of pentafluoroethane, but the distillation cost rises and distillation loss occurs. In addition to being economical, some chlorine-containing compounds form an azeotrope or azeotrope-like mixture with pentafluoroethane, and it is extremely difficult to separate the chlorine-containing compound only by distillation. is there. In particular, chloropentafluoroethane (CClF ₂ CF ₃ ) is usually contained in pentafluoroethane at a concentration of several thousand ppm or more, but pentafluoroethane and chloropentafluoroethane form an azeotrope, and are therefore usually used. Separation is difficult by the distillation operation, which is a separation and purification technique.

[0007]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and the present invention is a high-purity hexa hexadecene that can be used as an etching gas or a cleaning gas in the manufacturing process of semiconductor devices. An object of the present invention is to provide a method for industrially producing fluoroethane and its use.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a method for producing hexafluoroethane includes a chlorine-containing compound having 1 to 3 carbon atoms. Pentafluoroethane is reacted with hydrogen in the gas phase in the presence of a hydrogenation catalyst at 150 to 400 ° C. to hydrogenate the chlorine-containing compound, and the product of step (1) is used as a diluent gas. It was found that the above problems can be solved by using a production method including a step (2) of producing hexafluoroethane by reacting with fluorine in a gas phase in the presence of the substance, and completed the present invention. The present invention is a method for producing hexafluoroethane shown in the following [1] to [22] and its use.

[1] Pentafluoroethane containing a chlorine-containing compound having 1 to 3 carbon atoms is reacted with hydrogen in the gas phase at 150 to 400 ° C. in the presence of a hydrogenation catalyst to give the chlorine-containing compound. Step (1) of hydrogenating, and step (2) of reacting the product of step (1) with fluorine in the gas phase in the presence of a diluent gas to produce hexafluoroethane.
A method for producing hexafluoroethane, which comprises: [2] In the step (2), the product of the step (1) is purified pentafluoroethane obtained by distilling the crude product of the step (1). Production method. [3] The method for producing hexafluoroethane according to the above [1] or [2], which comprises a step of distilling the product obtained in step (2) to purify hexafluoroethane. [4] The method for producing hexafluoroethane according to any one of the above [1] to [3], which comprises a step of removing hydrogen chloride from the reaction product obtained in the step (1). [5] The chlorine-containing compound is at least one selected from the group consisting of chloromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and chlorotrifluoroethylene. The method for producing hexafluoroethane according to any one of the above [1] to [4], which is a compound.

[6] The hexa according to any one of the above [1] to [5], wherein in the step (1), the chlorine-containing compound contained in the pentafluoroethane containing the chlorine-containing compound is 1 vol% or less. Method for producing fluoroethane. [7] The method for producing hexafluoroethane according to the above [6], wherein in the step (1), the chlorine-containing compound contained in the pentafluoroethane containing the chlorine-containing compound is 0.5 vol% or less. [8] The method for producing hexafluoroethane according to any one of the above [1] to [7], wherein the hydrogenation catalyst in step (1) contains at least one element of the platinum group elements. [9] In the step (1), the hydrogenation catalyst is a catalyst in which at least one element of platinum group elements is supported on at least one carrier selected from the group consisting of activated carbon, alumina and fluorinated alumina. ] The manufacturing method of the hexafluoro ethane as described in. [10] In the step (1), hydrogen is in a molar ratio of 1 to 1 with respect to pentafluoroethane containing the chlorine-containing compound.
20. The method for producing hexafluoroethane according to any one of [1] to [9], which is 20.

[11] In step (2), step (1)
The content of trifluoroethane contained in the product of
The method for producing hexafluoroethane according to any one of the above [1] to [10], which is 1% or less. [12] Any of the above-mentioned [1] to [11], wherein in the step (2), the chlorine-containing compound having 1 to 3 carbon atoms contained in the product of the step (1) is 0.05 vol% or less. A method for producing hexafluoroethane according to Crab. [13] In the above [1] to [12], the diluent gas in step (2) is a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane and hydrogen fluoride. 6. A method for producing hexafluoroethane according to any one of the above. [14] The method for producing hexafluoroethane according to the above [13], wherein the diluent gas in the step (2) is a gas rich in hydrogen fluoride. [15] In step (2), the reaction temperature is 250 to 50.
The method for producing hexafluoroethane according to any one of the above [1] to [14], which is 0 ° C.

[16] The process for producing hexafluoroethane according to the above [15], wherein the reaction temperature in the step (2) is 350 to 450 ° C. [17] In the step (1), pentafluoroethane containing a chlorine-containing compound having 1 to 3 carbon atoms is a main component of pentafluoroethane obtained by reacting tetrachloroethylene or its fluoride with hydrogen fluoride. The method for producing hexafluoroethane according to any one of the above [1] to [16], which is a gas to be used. [18] The gas containing pentafluoroethane as a main component is
The method for producing hexafluoroethane according to the above [17], which is a gas obtained by distilling a gas obtained by reacting tetrachloroethylene or its fluoride with hydrogen fluoride. [19] A hexafluoroethane product obtained by using the production method according to any one of the above [1] to [18] and containing hexafluoroethane having a purity of 99.9997 vol% or more. [20] The content of the chlorine-containing compound is 1 volppm or less, and the content of pentafluoroethane is 1 volp.
The hexafluoroethane product according to the above [19], which is pm or less. [21] An etching gas containing the hexafluoroethane product according to the above [19] or [20]. [22] A cleaning gas containing the hexafluoroethane product according to the above [19] or [20].

That is, according to the present invention, "pentafluoroethane containing a chlorine-containing compound having 1 to 3 carbon atoms is reacted with hydrogen in the gas phase at 150 to 400 ° C. in the presence of a hydrogenation catalyst to obtain the above-mentioned inclusion. Step (1) of hydrogenating a chlorine compound,
And a step (2) for producing hexafluoroethane by reacting the product of step (1) with fluorine in a gas phase in the presence of a diluent gas "," a method for producing hexafluoroethane ", A hexafluoroethane product obtained by using the above-mentioned production method, characterized by containing hexafluoroethane having a purity of 99.9997 vol% or more "," characterized by containing the hexafluoroethane product Etching gas and cleaning gas "and the like.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing hexafluoroethane of the present invention will be described in detail below. The pentafluoroethane used in the present invention is generally produced by fluorinating perchlorethylene (CCl ₂ = CCl ₂ ) or its fluoride with hydrogen fluoride (HF), as described above. Fluoroethane contains chloromethane, chlorodifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, chlorotrifluoroethylene, etc. as chlorine-containing compounds derived from the starting materials. Be done. In order to purify pentafluoroethane containing these compounds to high purity, a method such as a known distillation operation is adopted, but the chlorine-containing compound and pentafluoroethane form an azeotropic mixture or an azeotrope-like mixture. Therefore, separation and purification are extremely difficult, and it is necessary to increase the number of distillation columns or the number of distillation columns, which causes a problem that the facility cost and energy cost are high and it is not economical.

The method for producing hexafluoroethane of the present invention is characterized by including the following steps (1) and (2). (1) Hydrogenating the chlorine-containing compound by reacting pentafluoroethane containing the chlorine-containing compound having 1 to 3 carbon atoms with hydrogen in the gas phase at 150 to 400 ° C. in the presence of a hydrogenation catalyst. Step (2) A step of producing hexafluoroethane by reacting the product of step (1) with fluorine in the gas phase in the presence of a diluent gas.

In the present invention, first, a chlorine-containing compound containing a chlorine atom in the molecule, which is contained as an impurity in pentafluoroethane, is mixed with hydrogen in the gas phase in the presence of a hydrogenation catalyst.
A step (1) of reacting at 50 to 400 ° C. to hydrogenate and converting into hydrofluorocarbon (HFC) or the like is performed.
For example, when chloropentafluoroethane (CF ₃ CClF ₂ ) or chlorotetrafluoroethane (CF ₃ CHClF) contained as impurities in pentafluoroethane is hydrogenated with hydrogen, it is represented by the following formula (1) or formula (2). The reaction takes place. CF ₃ CClF ₂ + H ₂ → CF ₃ CHF ₂ + HCl Formula (1) CF ₃ CHClF + H ₂ → CF ₃ CH ₂ F + HCl Formula (2) The product is a hydrofluorocarbon containing no chlorine atom and is a by-product. As a result, hydrogen chloride is produced.

The compounds which are converted into hydrofluorocarbons and the like by this hydrogenation reaction are the above-mentioned chloromethane, chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane. , Chlorotrifluoroethylene, etc., and these compounds are usually contained in pentafluoroethane in a total amount of several thousand volppm or more. When pentafluoroethane containing these compounds is directly reacted with fluorine gas, the methane-based compound is mainly converted to chlorotrifluoromethane, and the ethane-based compound is mainly converted to chloropentafluoroethane. Fluoroethane mainly contains chlorotrifluoromethane and chloropentafluoroethane as impurities.

Chloropentafluoroethane hardly reacts with fluorine gas at low temperatures. However, according to the study by the present inventors, for example, at a reaction temperature of 400 ° C., when the concentration of chloropentafluoroethane contained in pentafluoroethane is about 800 volppm or less, chloropentafluoroethane is cleaved and produced. The amount of chlorotrifluoromethane used is 1 volppm or less, but the concentration of chloropentafluoroethane is about 2000 volp.
If it exceeds pm, chlorotrifluoromethane is 2
Produces about volppm.

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

The chlorine-containing compound contained in pentafluoroethane used in the present invention is preferably 1 vol% or less, more preferably 0.5 vol% or less, and 0.3 vol% or less.
% Or less is more preferable. Chlorine-containing compound concentration is 1 vo
If it exceeds 1%, it is necessary to raise the reaction temperature and the life of the hydrogenation catalyst is shortened, which is not preferable.

As the hydrogenation catalyst in the step (1), a catalyst containing at least one element of the platinum group element is preferable, and platinum, palladium, rhodium, iridium, ruthenium and osmium can be used, and the raw material is , These metals, metal oxides or salts can be used. In addition, as the carrier that can be used for the catalyst, activated carbon, alumina and fluorinated alumina can be used, and the target reaction proceeds efficiently if the supporting rate of the above elements is 0.02% by mass or more. As the method for preparing the hydrogenation catalyst, for example, the above metal salt is dissolved in an aqueous solvent such as water, methanol or acetone, the above carrier is immersed, the necessary elements are adsorbed, and the solvent is further distilled off. It can be prepared by heat reduction treatment with hydrogen or the like.

The reaction temperature for the hydrogenation reaction in step (1) is 15
It is 0 to 400 ° C, preferably 200 to 300 ° C. When the reaction temperature is higher than 400 ° C, the catalyst life tends to be shortened, and an excessive reaction may proceed, which is not preferable. When the excess hydrogenation reaction proceeds, 1,1,1-trifluoroethane and the like are produced, which is not preferable. The step (2), which is a direct fluorination reaction of the organic compound and the fluorine gas, involves a very large heat of reaction, and for example, the more the C—H bond in the organic compound as the substrate is replaced with the C—F bond, the larger the number. The reaction heat becomes large and partial heat generation (hot spot) is likely to occur, which makes it difficult to control the reaction. Therefore, hydrofluorocarbons (HFCs) contained in pentafluoroethane, especially those having many C—H bonds
It is desirable to use pentafluoroethane which does not include 1,1-trifluoroethane as much as possible. On the other hand, if the reaction temperature is lower than 150 ° C., the desired reaction is difficult to proceed.

In the hydrogenation reaction of step (1), the molar ratio of hydrogen to the mixed gas (mixed gas containing hydrogen / chlorine-containing compound and pentafluoroethane) is preferably in the range of 1 to 20, more preferably in the range of 2 to 10. preferable. The reaction pressure is preferably in the range of atmospheric pressure to 1.5 MPa. If the reaction pressure exceeds 1.5 MPa, problems such as the need for pressure resistance of the apparatus occur, which is not preferable.

In the present invention, step (1) is carried out using the reaction conditions as described above, but the reaction product contains, in addition to pentafluoroethane, hydrofluorocarbon containing no chlorine atom and a trace amount of unreacted. It contains a chlorine compound and an acid component such as hydrogen chloride, which is a by-product, and it is desirable to remove this acid component.

As a method of removing the acid component, for example, a method of contacting with a purifying agent, a method of contacting with water or an aqueous alkali solution, etc. can be used. The gas from which the acid content has been removed is preferably dehydrated using a dehydrating agent such as zeolite, and then distilled prior to the direct fluorination step to obtain purified pentafluoroethane, and unreacted hydrogen is It is desirable to separate. If hydrogen is mixed in the step (2) of performing the direct fluorination reaction, it may react violently with fluorine gas, which is not preferable.

The total amount of chlorine-containing compounds contained in the mixed gas thus obtained through the step (1) is 0.05 v.
It is preferably ol% or less and 1,1,1-trifluoroethane is preferably 0.2 vol% or less.

Next, the step (2) of reacting the gas containing pentafluoroethane as a main component with the fluorine gas obtained through the step (1) will be described. The step (2) is performed in the presence of a diluting gas, and the mixed gas containing pentafluoroethane as a main component is set to a concentration below the explosion range. Specifically, the concentration of pentafluoroethane at the reactor inlet is preferably about 6 mol% or less. As the dilution gas, a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane and hydrogen fluoride is used,
A diluent gas rich in hydrogen fluoride is preferably used. Diluent gas rich in hydrogen fluoride means hydrogen fluoride of 50 mol%
It means a dilution gas containing the above.

The amount of fluorine gas used is the molar ratio (F ₂ / F) of the mixed gas containing pentafluoroethane as a main component.
The pentafluoroethane containing hydrogenated compound is preferably in the range of 0.5 to 2.0, more preferably 0.9 to 1.3. Reaction temperature is 250-50
0 degreeC is preferable and 350-450 degreeC is more preferable.
When the reaction temperature is higher than 500 ° C., the target hexafluoroethane is cleaved and tetrafluoromethane (C
F ₄ ) may be generated, which is not preferable. Also,
If the reaction temperature is lower than 250 ° C., the reaction progresses slowly, which is not preferable.

The method for purifying the gas distilled after the step (2) is not particularly limited, but it is preferable to first remove the residual unreacted fluorine gas. For example, trifluoromethane, which is a hydrofluorocarbon, is added and reacted with excess fluorine gas to remove it. It is preferable to further distill, for example, first, hydrogen fluoride and an organic substance are separated. The separated hydrogen fluoride is processed in step (2)
It can be reused as a diluent gas for the direct fluorination reaction of, and can also be used for other purposes.

Here, the composition of the gas containing the separated organic matter greatly differs depending on the diluent gas used in the reaction. For example, when a gas rich in hydrogen fluoride or the same hexafluoroethane as the target is used as the diluent gas, The gas obtained by the reaction contains hexafluoroethane as a main component. Further, when tetrafluoromethane or octafluoropropane is used as the diluting gas, distillation is performed again for purification, but in any case, high-purity hexafluoroethane can be obtained by repeating distillation of the mixed gas obtained. Obtainable.

Distillation purification of the mixed gas obtained by the reaction depends on the composition ratio, but for example, low boiling point components such as inert gas and tetrafluoromethane are extracted from the top of the first distillation column, and the bottom part is extracted. A mixed gas containing hexafluoroethane as a main component is extracted. The mixed gas withdrawn from the bottom is introduced into the second distillation column, the inert gas and low-boiling components such as trifluoromethane are withdrawn from the top of the second distillation column, and the hexadecane extracted from the bottom is removed. The mixed gas containing fluoroethane as the main component is the third
Can be purified by extracting the high-purity hexafluoroethane from the top of the column.

Hexafluoroethane purified in this manner contains almost no impurities, and high-purity hexafluoroethane can be obtained. Its purity is 9
The content of the chlorine-containing compound, which is 9.9997 vol% or more and is included as an impurity, is 1 volppm or less, and pentafluoroethane is also 1 volppm or less. As a method for analyzing hexafluoroethane having a purity of 99.9997 vol% or more, TCD method of gas chromatograph (GC), FID method (including precut method), ECD method or gas chromatograph mass spectrometer (GC-MS) is used. ) Etc. can be used.

Next, the use of hexafluoroethane obtained by using the production method of the present invention will be described. High-purity hexafluoroethane or a mixed gas with an inert gas such as He, N ₂ , Ar or the like, O ₂ , NF ₃ or the like (in the present invention, collectively referred to as “hexafluoroethane product”) is a semiconductor. It can be used as an etching gas in the etching process in the device manufacturing process.
It can also be used as a cleaning gas in the cleaning process in the semiconductor device manufacturing process. In a manufacturing process of a semiconductor device such as an LSI or a TFT, a thin film or a thick film is formed by using a CVD method, a sputtering method, an evaporation method, or the like, and etching is performed to form a circuit pattern. Further, in an apparatus for forming a thin film or a thick film, cleaning is performed to remove unnecessary deposits deposited on the inner walls of the apparatus, jigs and the like. This is because generation of unnecessary deposits causes the generation of particles, and it is necessary to remove them at any time in order to manufacture a good quality film.

The etching method using hexafluoroethane can be carried out under various dry etching conditions such as plasma etching and microwave etching. Hexafluoroethane and an inert gas such as He, N ₂ or Ar, or HCl or O _{2 is used.} , H _{2 and the} like gas may be mixed at an appropriate ratio and used.

[0035]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Pentafluoroethane Production Example 1] (Raw Material Example 1) Tetrachloroethylene (CCl ₂ = CCl ₂ ) was brought into contact with Molecular Sieves 4A (manufactured by Union Showa Co., Ltd.) to obtain a stabilizer and water contained in tetrachloroethylene. Was removed, and then reacted with hydrogen fluoride (HF) in the presence of a chromium-based fluorination catalyst (first reaction: reaction pressure 0.4
MPa, reaction temperature 300 ° C., HF / tetrachloroethylene = 8 (molar ratio)). Then, mainly dichlorotrifluoroethane (CF ₃ CHCl ₂ ) obtained in the first reaction
And a mixed gas containing chlorotetrafluoroethane (CF ₃ CHClF) were reacted with hydrogen fluoride (second reaction: reaction pressure 0.4 MPa, reaction temperature 330 ° C., HF / (CF
₃ CHCl ₂ + CF ₃ CHClF) = 6 (molar ratio). Second
After the completion of the reaction, the acid content was removed by a known method, and distillation purification was performed to obtain a distillate mainly containing pentafluoroethane as a main component. When this distillate was analyzed using a gas chromatograph, it was a mixed gas (raw material example 1) having the composition shown in Table 1.

[0037]

[Table 1]

Production Example 2 of Pentafluoroethane (Raw Material Example 2) The mixed gas containing pentafluoroethane as the main component (Raw Material Example 1) obtained by the above method is distilled by a known method. It was When the distillate was analyzed using a gas chromatograph, it was a mixed gas (raw material example 2) having the composition shown in Table 2.

[0039]

[Table 2]

[Catalyst Production Example 1] (Catalyst Example 1) Sodium primary palladium chloride was dissolved in water, and a spherical alumina carrier having a diameter of 1.6 mm was immersed therein to adsorb a palladium salt. Evaporate the solvent at temperature, 3
After air calcination at 00 ° C, hydrogen reduction was performed at 350 ° C. The palladium loading of the resulting catalyst was 2.0%.

[Catalyst Production Example 2] (Catalyst Example 2) Dichloroplatinic acid was dissolved in water and a spherical alumina carrier having a diameter of 1.6 mm was immersed therein to adsorb a platinum salt, and then 10
The solvent was distilled off at a temperature of 0 ° C., air baking was performed at 300 ° C., and then hydrogen reduction was performed at 350 ° C. The platinum loading rate of the obtained catalyst was 2.0%.

Example 1 100 ml of catalyst (Catalyst example 1) was placed in an Inconel 600 type reactor having an inner diameter of 1 inch and a length of 1 m.
Was charged and the temperature was maintained at 280 ° C. while flowing nitrogen gas. Next, hydrogen was supplied at a flow rate of 0.36 NL / hr, a mixed gas having the composition shown in Table 1 (raw material example 1) was supplied at a flow rate of 8.33 NL / hr, and then nitrogen gas was supplied. The reaction was stopped and the reaction (step (1)) was started. After 2 hours, the outlet gas from the reactor was washed with an aqueous solution of potassium hydroxide to remove the acid content, and then the gas composition was analyzed by gas chromatography to find that pentafluoroethane having the composition shown in Table 3 was mainly contained. It was a mixed gas as an ingredient.

[0043]

[Table 3]

The mixed gas containing pentafluoroethane as the main component having the composition shown in Table 3 obtained by the above-mentioned method was distilled by a known method to remove low boiling point components such as inert gas and hydrogen gas, A direct fluorination reaction with fluorine gas (step (2)) was performed.

An Inconel 600 type reactor having an inner diameter of 20.6 mmΦ and a length of 500 mm (electric heater-heating: the reactor was passivated with fluorine gas at a temperature of 500 ° C.),
Nitrogen gas was supplied from the two gas inlets at a flow rate of 30 NL / hr in total, and the temperature of the reactor was maintained at 420 ° C. Next, hydrogen fluoride was caused to flow from the two gas introduction ports at a total flow rate of 50 NL / hr, and a mixed gas containing pentafluoroene as a main component in which the low boiling point components were cut was introduced from one gas introduction port. It was introduced at a flow rate of 3.5 NL / hr.
Fluorine gas was introduced from the other gas introduction port at a flow rate of 3.85 NL / hr to carry out the reaction. After 3 hours, the outlet gas from the reactor was brought into contact with an aqueous potassium hydroxide solution and an aqueous potassium iodide solution to remove hydrogen fluoride and unreacted fluorine gas. Then it is dried by contact with a dehydrating agent,
The composition of the dried gas was analyzed by gas chromatography. The analysis results are shown in Table 4.

[0046]

[Table 4]

The dried gas mainly containing hexafluoroethane was collected by cooling and purified by distillation.
The gas after purification is gas chromatograph TCD method, FI
Analysis by D method, ECD method and GC-MS method,
The results are shown in Table 5.

[0048]

[Table 5] As is clear from the analysis results shown in Table 5, hexafluoroethane contains almost no other impurities, and high-purity hexafluoroethane is obtained. Its purity is 99.
It can be seen that it is 9997 vol% or more.

(Example 2) The catalyst of (Catalyst example 2) was added to 100
The reaction (step (1)) was carried out under the same conditions and operations as in Example 1 except that the reaction mixture was charged in ml and the mixed gas of (Material Example 2) was used. The reactor outlet gas was analyzed after the same treatment, and the analysis results are shown in Table 6.

[0050]

[Table 6]

The mixed gas containing pentafluoroethane as a main component having the composition shown in Table 6 obtained by the above method was distilled by a known method to remove low boiling point components such as inert gas and hydrogen. A direct fluorination reaction with fluorine gas (step (2)) was performed under the same conditions and operations as in Example 1. The gas obtained by treating the outlet gas from the reactor in the same manner as in Example 1 was analyzed by gas chromatography, and the analysis results are shown in Table 7. The reaction was carried out under the same conditions and operations as in Example 3 except for pentafluoroethane as a raw material. Table 8 shows the results of gas composition analysis by gas chromatography.

[0052]

[Table 7]

Next, the mixed gas containing hexafluoroethane as a main component was collected by cooling, purified by distillation, and the purified gas was analyzed. As a result, the purity of hexafluoroethane was 99.9998 vol% or more. The content of chlorine-containing compounds contained as impurities is less than 1 volppm, and the content of pentafluoroethane as a raw material is also 1 vo
It was less than 1 ppm.

(Comparative Example 1) Step (1) The reaction (step (1)) was performed and analyzed under the same conditions and operations as in Example 1 except that the reaction temperature was 430 ° C. The analysis results are shown in Table 8.

[0055]

[Table 8] As is clear from the analysis results shown in Table 8, when step (1) is carried out at a reaction temperature higher than 400 ° C., excess hydrogenation reaction proceeds, and the amount of 1,1,1-trifluoroethane produced is increased. Significantly increased. In addition, methane and ethane were also generated, and deterioration of the catalyst was observed.

Comparative Example 2 Step (1) The reaction (step (1)) was conducted under the same conditions and operations as in Example 1 except that the reaction temperature was 130 ° C., and an analysis was conducted. When step (1) was carried out at a reaction temperature lower than 150 ° C., the hydrogenation reaction of the chlorine-containing compound hardly proceeded, and the conversion rate of chloropentafluoroethane was about 19%.

(Comparative Example 3) Step (2) A direct fluorination reaction (Step (2)) was carried out under the same conditions and operations as in Example 1 except that the mixed gas of (Material Example 1) was used. After removing hydrogen fluoride and unreacted fluorine gas contained in the outlet gas of the vessel, analysis was performed using a gas chromatograph. The analysis results are shown in Table 9.

[0058]

[Table 9] As is apparent from Table 9, it is found that when the direct fluorination reaction is performed using pentafluoroethane having a high concentration of the chlorine-containing compound, chlorotrifluoromethane, which is a difficult-to-separate substance, is produced.

[0059]

As described above, high-purity hexafluoroethane can be obtained by using the production method of the present invention. Hexafluoroethane obtained by the method of the present invention can be used as an etching gas or a cleaning gas in the semiconductor device manufacturing process.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C11D 7/50 C11D 7/50 H01L 21/3065 C07B 61/00 300 // C07B 61/00 300 H01L 21 / 302 FF term (reference) 4H003 DA15 ED21 FA45 4H006 AA02 AC11 AC30 AD11 BC10 BC13 BC31 BD10 BE20 BE53 EA02 4H039 CA19 CD20 5F004 AA13 DA00

Claims (22)

[Claims] 1. Pentafluoroethane containing a chlorine-containing compound having 1 to 3 carbon atoms in the presence of a hydrogenation catalyst,
Step (1) of hydrogenating the chlorine-containing compound by reacting with hydrogen in the gas phase at 150 to 400 ° C., and reacting the product of step (1) with fluorine in the gas phase in the presence of a diluent gas. A method for producing hexafluoroethane, comprising the step (2) of producing hexafluoroethane. 2. The hexafluoroethane according to claim 1, wherein in step (2), the product of step (1) is purified pentafluoroethane obtained by distilling the crude product of step (1). Manufacturing method. 3. Distilling the product obtained in step (2),
The method for producing hexafluoroethane according to claim 1 or 2, which comprises a step of purifying hexafluoroethane. 4. The method for producing hexafluoroethane according to claim 1, which comprises a step of removing hydrogen chloride from the reaction product obtained in step (1). 5. The at least one chlorine-containing compound is selected from the group consisting of chloromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane and chlorotrifluoroethylene. The method for producing hexafluoroethane according to any one of claims 1 to 4, which is a compound of species. 6. The production of hexafluoroethane according to claim 1, wherein in the step (1), the chlorine-containing compound contained in the pentafluoroethane containing the chlorine-containing compound is 1 vol% or less. Method. 7. The method for producing hexafluoroethane according to claim 6, wherein in the step (1), the chlorine-containing compound contained in pentafluoroethane containing the chlorine-containing compound is 0.5 vol% or less. 8. The method for producing hexafluoroethane according to claim 1, wherein the hydrogenation catalyst in step (1) contains at least one element of the platinum group elements. 9. In the step (1), the hydrogenation catalyst is a catalyst in which at least one element of the platinum group element is supported on at least one carrier selected from the group consisting of activated carbon, alumina and fluorinated alumina. Item 9. A method for producing hexafluoroethane according to Item 8. 10. The hexafluoroethane according to claim 1, wherein in step (1), hydrogen is 1 to 20 in molar ratio with respect to pentafluoroethane containing the chlorine-containing compound. Production method. 11. In the step (2), 0.2 vol% of trifluoroethane contained in the product of the step (1).
It is the following, The manufacturing method of the hexafluoro ethane in any one of Claims 1-10. 12. The chlorine-containing compound having 1 to 3 carbon atoms contained in the product of step (1) in step (2) is 0.05 vol% or less. The method for producing hexafluoroethane according to 1. 13. The method according to claim 1, wherein the diluent gas in step (2) is a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane and hydrogen fluoride. A method for producing hexafluoroethane according to Crab. 14. The method for producing hexafluoroethane according to claim 13, wherein the diluent gas in step (2) is a gas rich in hydrogen fluoride. 15. The reaction temperature is 25 in step (2).
The method for producing hexafluoroethane according to any one of claims 1 to 14, which has a temperature of 0 to 500 ° C. 16. The reaction temperature is 35 in step (2).
The method for producing hexafluoroethane according to claim 15, wherein the temperature is 0 to 450 ° C. 17. In the step (1), pentafluoroethane containing a chlorine-containing compound having 1 to 3 carbon atoms is pentafluoroethane obtained by reacting tetrachloroethylene or its fluoride with hydrogen fluoride. The method for producing hexafluoroethane according to any one of claims 1 to 16, which is a gas containing a main component. 18. The hexa according to claim 17, wherein the gas containing pentafluoroethane as a main component is a gas obtained by distilling a gas obtained by reacting tetrachloroethylene or its fluoride with hydrogen fluoride. Method for producing fluoroethane. 19. Obtained using the production method according to any one of claims 1 to 18, and having a purity of 99.9997% by volume.
A hexafluoroethane product containing the above hexafluoroethane. 20. The content of the chlorine-containing compound is 1 vol.
ppm or less and the content of pentafluoroethane is 1
The hexafluoroethane product according to claim 19, which has a volppm or less. 21. An etching gas containing the hexafluoroethane product according to claim 19 or 20. 22. A cleaning gas containing the hexafluoroethane product of claim 19 or 20.