KR20020019589A - Process for producing hexafluoroethane and use thereof - Google Patents

Abstract

The present invention aims at providing a profitable CF ₃ CF ₃ production method and its use by using CF ₃ CHF ₂ containing a compound having a chlorine atom in a molecule.

In the process of the present invention, a mixed gas containing CF ₃ CHF ₂ and a compound having a chlorine atom in a molecule is reacted with hydrogen fluoride in the presence of a fluorination catalyst, whereby CClF ₂ CF _{3, which} is a main impurity, is reacted with CF ₃ CF ₃ And CF ₃ CHF ₂ containing CF ₃ CF ₃ reacts with gaseous fluorine gas in the presence of a diluting gas.

Description

PROCESS FOR PRODUCING HEXAFLUOROETHANE AND USE THEREOF BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing hexafluoroethane,

Pentafluoroethane (hereinafter referred to as "CF ₃ CHF ₂ ") is used, for example, as a low temperature refrigerant or as a starting material for the production of hexafluoroethane (hereinafter referred to as "CF ₃ CF ₃ ").

For the manufacture of CF ₃ CHF _2, for example, the following methods are known so far.

(1) perchlorate of ethylene (CCl ₂ = CCl _2), or hydrogen fluoride and a fluorination method for its fluoride (JP-A-597724 (JP -A is here, refers to Japanese Laid-Open Patent Publication.), JP-A- 6-506221, JP-A-7-76534, JP-A-7-118182, JP-A-8-268932 and JP-A-9-511515)

(2) a method of performing hydrolysis of chloropentafluoroethane (CClF ₂ CF ₃ ) and

(3) A method of reacting halogen-containing ethylene with fluorine gas (JP-A-1-38034).

When using these methods for the production of CF ₃ CHF ₂ , the target CF ₃ CHF ₂ contains a compound that retains a chlorine atom in the molecule as a major impurity. Examples of the compound having a chlorine atom in the molecule include compounds having one carbon atom in the molecule such as chloromethane, chlorodifluoromethane and chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoro Ethane, and chlorotrifluoroethane, and unsaturated compounds such as chlorotrifluoroethylene. These compounds may be used alone or in combination of two or more.

When CF ₃ CHF ₂ contains a compound having a chlorine atom in its molecule, when CF ₃ CF ₃ is produced by a direct fluorination reaction of a fluorine gas (F ₂ ) with a CF ₃ CHF ₂ reaction, chlorine, Other types of chlorine fluoride or chlorofluorocarbon react with fluorine gas. No particular problem occurs even when hydrofluorocarbons (HFC) or perfluorocarbons (PFC) are contained in CF ₃ CHF ₂ , but for example, chloromethane (CH ₃ Cl) or chlorodifluoromethane ₂ ) reacts with fluorine gas to produce chlorotrifluoromethane (CClF ₃ ). Since the objective CF ₃ CF ₃ and chlorotrifluoromethane form an azeotropic mixture, it is difficult to remove CClF ₃ even if distillation, adsorption or the like is carried out for purification. Therefore, when fluorine gas and CF ₃ CHF ₂ are reacted to generate CF ₃ CF _3, the amount of the compound having a chlorine atom in the molecule contained in CF ₃ CHF ₂ should be reduced as much as possible.

The total amount of the compound having a chlorine atom in the molecule is sometimes 1 vol% depending on the conventional production method of CF ₃ CHF ₂ . Therefore, distillation operation is CF ₃ CHF is repeated in order to remove these compounds are contained in the _second, increased purity of the CF ₃ CHF _2, but this increases the distillation costs, and the distillation loss being caused, profitability or falls, the molecular Some of the compounds having a chlorine atom in them have such problems that it is very difficult to form an azeotropic or azeotrope mixture with CF ₃ CHF ₂ and to remove only by a distillation operation. Particularly, chloropentafluoroethane (hereinafter referred to as " CClF ₂ CF ₃ ") is generally contained in CF ₃ CHF _{2 at a} concentration of several thousand ppm or more, but the azeotropic mixture is formed by CF ₃ CHF ₂ and CClF ₂ CF ₃ It is difficult to separate by distillation which is a commonly used separation and purification method.

Several methods have been proposed to separate CClF ₂ CF ₃ contained in CF ₃ CHF ₂ . for example,

(1) CF ₃ CHF ₂ and CClF ₂ CF by the addition of a third component to a mixture of ₂ how to perform extractive distillation (JP-A-6-510980, JP -A-7-133240, JP-A-7- 258123, JP-A-8-3082, JP-A-8-143486 and JP-A-10-513190)

(2) a method of removing CClF ₂ CF ₂ contained in CF ₃ CHF ₂ using an adsorbent (see JP-A-6-92879 and JP-W-8-508479 ("JP-W" )) And

(3) under the presence of CF ₃ CHF ₂ CF ₂ CClF a method for switching to the _{CF 3 CHF 2 (JP-A} -7-509238, JP-A-8-40949, JP-A-8 contained in the _second of a hydrogenation catalyst -301801 and JP-A-10-87525).

However, in these methods, the method (1) requires a step of recovering the third component from a mixture of CClF ₂ CF ₃ and the third component, and the method (2) requires a step of regenerating the adsorbent And the method (3) has a problem that the catalyst life is shortened due to the generated hydrogen chloride.

The present invention has been made in view of this situation, and an object of the present invention is to provide a method for producing profitable CF ₃ CF ₃ by using a gas mixture containing CF ₃ CHF ₂ , And a method for producing CF ₃ CF ₃ used as a flushing gas, and to provide a use thereof.

This application claims benefit under 35 USC §119 (e) (1) of the filing date of Provisional Application No. 60 / 230,806, filed September 7, 2000, pursuant to 35 USC § 111 (b) Filed in the United States.

The present invention relates to a process for the production of fluorinated fluorinated compounds by reacting a gas mixture containing pentafluoroethane and a chlorine atom in the presence of a fluorination catalyst and a gaseous hydrogen fluoride in the presence of a fluorination catalyst to fluorinate the chlorine atom- Reacting a gaseous mixture containing a compound with a gaseous fluorine gas in the presence of a diluent gas, and to the use of the hexafluoroethane.

In order to solve the above problems, the inventors of the present invention have found that a gas mixture containing CF ₃ CHF ₂ and a compound having a chlorine atom in the molecule as an impurity in a process for producing CF ₃ CF ₃ To convert the CClF ₂ CF ₃ contained in the gas mixture to CF ₃ CF ₃ and subsequently the resulting gas mixture containing CF ₃ CHF ₂ and CF ₃ CF ₃ is reacted with gaseous It has been found that the above problems can be solved when a direct fluorination reaction is carried out by reacting with fluorine gas. The present invention has been achieved on the basis of this finding. The present invention provides a process for producing CF ₃ CF ₃ and its use as described in the following (1) to (19).

[One]. The process for the production of hexafluoroethane comprises the following two steps.

(1) reacting a gas mixture containing pentafluoroethane and a compound having a chlorine atom with gaseous hydrogen fluoride in the presence of a fluorination catalyst to fluorinate the compound having the chlorine atom; And

(2) reacting the gaseous mixture containing pentafluoroethane and the fluorinated compound obtained in the step (1) with gaseous fluorine gas in the presence of a diluting gas.

[2]. In the method for producing hexafluoroethane according to [1], the compound having a chlorine atom may be at least one selected from the group consisting of chloromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, Chlorotrifluoroethane, and chlorotrifluoroethylene. ≪ Desc / Clms Page number 7 >

[3]. In the method for producing hexafluoroethane according to [1] or [2], the total amount of the compound having a chlorine atom contained in the gas mixture in the step (1) is 1 vol% or less.

[4]. In the method for producing hexafluoroethane according to [1] or [2], the total amount of the compound having a chlorine atom contained in the gas mixture in the step (1) is 0.5% by volume or less.

[5]. In the method for producing hexafluoroethane according to [1] or [2], the fluorination catalyst in the step (1) is a bulk catalyst obtained by adding indium to chromium oxide.

[6]. In the method for producing hexafluoroethane according to [1] or [2], the temperature for the reaction with hydrogen fluoride in the presence of the fluorination catalyst in the step (1) is in the range of 150 to 480 캜.

[7]. In the method for producing hexafluoroethane according to [1] or [2], the molar ratio of the hydrogen fluoride / organic substance contained in the gas mixture in the step (1) is in the range of 0.5 to 5.

[8]. In the method for producing hexafluoroethane described in [1] or [2], the step of removing the acid content contained in the produced hydrogen chloride is carried out before the step (2).

[9]. A process for producing hexafluoroethane according to [1] or [2], comprising the steps of: separating chlorotetrafluoroethane and / or chlorotrifluoroethane; and separating chlorotetrafluoroethane and / or chlorotrifluoroethane The step of restoring the roe-tan to the step (1) is performed before the step (2).

[10]. In the method for producing hexafluoroethane according to [1] or [2], the total amount of the compound having a chlorine atom contained in the gas mixture in the step (2) is 0.02% by volume or less.

[11]. In the method for producing hexafluoroethane according to [1] or [2], the fluorinated compound contained in the gas mixture in the step (2) is mainly composed of hexafluoroethane.

[12]. The method for producing hexafluoroethane according to [1] or [2], wherein the diluent gas in the step (2) is selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane and hydrogen fluoride It is a gas containing at least one selected.

[13]. In the method for producing hexafluoroethane according to [1] or [2], the diluent gas in the step (2) is a gas rich in hydrogen fluoride.

[14]. In the method for producing hexafluoroethane according to [1] or [2], the temperature during the reaction of the gas mixture containing the fluorinated compound in the step (2) with the fluorine gas is in the range of 250 to 500 ° C .

[15]. In the method for producing hexafluoroethane according to [1] or [2], the temperature during the reaction of the fluorine compound with the gas mixture containing the fluorinated compound in the step (2) is in the range of 350 to 450 ° C .

[16]. Is a hexafluoroethane product containing hexafluoroethane having a purity of at least 99.9997 vol%.

[17]. In the hexafluoroethane product described in [16], the content of the compound having a chlorine atom is 1 ppm by volume or less, and the content of pentafluoroethane is 1 ppm by volume or less.

[18]. The etching gas contains the hexafluoroethane product described in [16] or [17].

[19]. The flushing gas contains the hexafluoroethane product described in [16] or [17].

In summary, the present invention relates to a process wherein a gas mixture containing CF ₃ CHF ₂ and a compound having a chlorine atom is reacted with gaseous hydrogen fluoride in the presence of a fluorination catalyst to fluorinate the compound having the chlorine atom and a step of CF ₃ CF ₃ CF ₃ production method comprising reacting a gaseous mixture containing CHF ₂ and the fluorinated compound obtained in the above step with gaseous fluorine gas in the presence of a diluting gas "," CF ₃ CF _{3 having a} purity of 99.9997 vol% provides a CF ₃ CF ₃ CF ₃ product "," an etching gas containing the CF ₃ CF ₃ product containing "and" cleaning gas containing the CF ₃ CF ₃ product ".

The process for producing CF ₃ CF ₃ according to the present invention and its use are described below.

As noted above, CF ₃ CHF ₂ for use in the present invention is generally produced by perchlorate ethylene (CCl ₂ = CCl ₂ ) or hydrogen fluoride and its fluorine fluorination, CF ₃ CHF ₂ is chloromethane, Containing chlorine atoms derived from a starting material such as chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, and chlorotrifluoroethane. . In order to make the purity of the CF ₃ CHF ₂ contained in these compounds high purity, known methods by distillation are employed, but these methods are not suitable for fractionation because the compound and CF ₃ CHF ₂ form an azeotrope or azeotrope mixture Purification is very difficult and this problem is not economical because the number of distillation columns or the number of distillation columns is increased to increase the device or energy cost.

In the present invention, a compound having chlorine atoms contained in CF ₃ CHF ₂ as an impurity is fluorinated with hydrogen fluoride by raising the temperature in the presence of a fluorination catalyst, whereby hydrofluorocarbons (HFC) or perfluorocarbons ). For example, it is represented by the following general formula (1) or (2) that CClF ₂ CF ₃ or chlorotetrafluoroethane contained as an impurity in CF ₃ CHF ₂ is fluorinated by using hydrogen fluoride.

CF ₃ CClF ₂ + HF - > CF ₃ CF ₃ + HCl (1)

CF ₃ CHClF + HF? CF ₃ CHF ₂ + HCl (2)

The product is HFC or PFC without chlorine atoms, and hydrogen chloride is produced as a by-product.

In the present application, a mixed gas containing CF ₃ CHF ₂ and a compound having a chlorine atom is sometimes referred to as a " starting gas mixture ".

In this fluorination reaction, compounds which convert to HFC or PFC are chloromethane, chlorodifluoromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane and chlorotrifluoro Ethane. These compounds are generally contained in CF ₃ CHF ₂ in a total amount of several thousand ppm or more. When the starting gas mixture containing these compounds reacts with fluorine gas, the methane-type compounds convert to CClF ₃ and the ethane-type compounds convert to CClF ₂ CF ₃ , so that CF ₃ CF ₃ obtained after the reaction is a major impurity, ₂ and CClF ₂ CF ₃ .

CClF ₂ CF ₃ hardly reacts with fluorine gas at low temperatures. However, according to the investigations by the present inventors, for example, the amount of CClF ₃ produced by the decomposition of CClF ₂ CF ₃ at a reaction temperature of 400 ° C is 1 ppm when the concentration of CClF ₂ CF ₃ contained in the starting gas mixture is less than about 800 ppm or less, about 2ppm of CClF ₃ is generated when the concentration of CF ₃ CClF ₂ exceeds about 2,000ppm. Since CClF ₃ forms an azeotropic mixture with CF ₃ CF ₃ , it is difficult to remove the compound by distillation, adsorption, or the like to purify the compound even though the concentration is low. Therefore, it is preferable that the CClF ₃ compound produced by reacting with the fluorine gas not only needs to be removed from CF ₃ CHF ₂ , which is a starting material, but also that the CClF ₂ CF ₃ content is reduced as low as possible.

The total amount of the compound having a chlorine atom contained in the starting gas mixture for use in the present invention is preferably 1 vol% or less, more preferably 0.5 vol% or less, and further preferably 0.3 vol% or less. If the concentration of the compound having a chlorine atom is more than 1% by volume, the reaction must be carried out at a high temperature, the lifetime of the fluorination catalyst becomes unfavorably short, side reactions occur simultaneously, and the productivity decreases.

The fluorination catalyst contains one or more elements selected from the group consisting of chromium, nickel, zinc, indium and gallium, and may be a known catalyst such as a supported catalyst or a bulk catalyst.

In the case of supported catalysts, the carrier is preferably alumina and / or partially fluorinated alumina, and the support ratio is preferably 30 wt% or less. In the case of the bulk catalyst, in particular, it is preferable that chromium is contained as a main component, and the atomic ratio of nickel, zinc, indium and / or gallium: chromium is 0.01: 0.6. In the present invention, a bulk catalyst obtained by adding indium to an oxide of chromium is most preferable.

In the fluorination step of the compound having a chlorine atom, the reaction temperature is preferably 150 to 480 ° C. If the reaction temperature is higher than 480 DEG C, for example, the reaction causes adverse effects such as deterioration of the catalyst or side reaction, which is not preferable. Although it depends on the change of the concentration of the compound contained in the starting gas mixture, it is preferable that the reaction temperature can be selected depending on the kind of the compound. For example, in the reaction of CClF ₂ CF ₃ shown in the general formula (1), the reaction temperature is preferably 400 ° C. or higher, and in the reaction of CH ₃ CHClF shown in the general formula (2), the reaction temperature is preferably 300 ° C. or higher.

In the case of the reaction of hydrogen fluoride with chlorodifluoromethane (CHClF ₂ ), the reaction represented by the following general formula (3) is obtained.

CHClF ₂ + HF - > CHF ₃ + HCl (3)

In this reaction, the reaction temperature is preferably 150 ° C or higher, and if the reaction temperature exceeds 400 ° C, the reaction is adversely affected.

In the fluorination step of a compound having a chlorine atom, the reaction temperature sometimes changes depending on the kind of the following compounds. Therefore, it is preferable to use two or more reaction apparatuses, but even one reaction apparatus is generally sufficient when a plurality of compounds each have a different optimum reaction temperature range or a high concentration of each compound.

The amount of HF used is preferably 0.5 to 5, more preferably 0.5 to 2, depending on the molar ratio of the starting gas mixture containing CF ₃ CHF ₂ (HF / organic) to the organics. If the molar ratio is less than 0.5, the reaction is difficult to proceed, whereas if it exceeds 5, a large-scale reactor is required and this is not advantageous.

In addition, in the fluorination step of the compound having a chlorine atom, the reaction pressure is preferably 1.5 MPa at atmospheric pressure. Above 1.5 MPa, the devices require an unfavorable pressure resistance.

In the present invention, the reaction with hydrogen fluoride is carried out in the presence of a fluorination catalyst using the following reaction conditions, followed by chlorine-free impurities mainly containing CF ₃ CHF ₂ , HFC or PFC and hydrogen chloride as a by-product contained in the reaction product . In the case of CF ₃ CHF ₂ , when the reaction temperature becomes high, hydrogen chloride and a side reaction proceed further as shown in the following general formula (4).

CF ₃ CHF ₂ + HCl - > CF ₃ CHClF + HF (4)

In the case where 1,1,1,2-tetrafluoroethane is contained, the hydrogen chloride and the side reaction proceed further as shown by the following general formula (5).

CF ₃ CH ₂ F + HCl - > CF ₃ CH ₂ Cl + HF (5)

Therefore, it is preferable that, after the fluorination in the step (1), the acid content of the produced hydrogen chloride is removed.

The acid content is removed to remove unreacted hydrogen fluoride (excess hydrogen fluoride) and byproduct hydrogen chloride. Although hydrogen fluoride does not have a direct adverse effect on the fluorination reaction step, it is preferable that hydrogen chloride is removed because it occasionally causes adverse effects such as formation of a chlorine-containing compound or chlorine fluoride as shown in the general formula (4) or (5) . The step of removing the acid content is carried out before the direct fluorination step. Examples of acid content removal methods include:

(1) a method in which, when a large amount of unreacted hydrogen fluoride is contained, introducing a discharge containing an acidic content into the distillation column, extracting hydrogen chloride from the top of the column, and extracting organic substances and hydrogen fluoride from the column bottom,

(2) contacting the produced hydrogen chloride and unreacted hydrogen fluoride with a cleaning agent, and

(3) Method of washing the acid content with water or alkaline water

.

In the present invention, the method of removing the acid content is not particularly limited. For example, the method (3) can be used. The alkali used there may be an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide and the like. The absorbed hydrogen fluoride can be recovered and reused, and the gas that has passed through the cleaning liquid is dehydrated using a dehydrating agent such as zeolite.

The gas mainly containing CF ₃ CHF ₂ contains HCFC or CFC, which is not fully fluorinated by reaction with hydrogen fluoride, as an impurity and sometimes passes through an acid removal step. In this case, the HCFC or CFC is directly subjected to a fluorination reaction It is preferred that it is removed by distillation before the step.

The main compounds that may be contained in CF ₃ CHF ₂ and CF ₃ CHF ₂ are shown in Table 1, together with their respective boiling points.

Compound name constitutional formula Boiling point (℃) Tetrafluoromethane CF ₄ -128 Trifluoromethane CHF ₃ -84 Hexafluoroethane CF ₃ CF ₃ -78.1 Pentafluoroethane CF ₃ CHF ₂ -48.5 Chloropentafluoroethane CF ₃ CClF ₂ -38.7 2-chloro-1,1,1,2-tetrafluoroethane CF ₃ CHClF -12 2-chloro-1,1,1-trifluoroethane CF ₃ CH ₂ Cl 6.1

The gas mainly containing CF ₃ CHF ₂ is introduced into the distillation column and then CF ₄ , CHF ₃ , CF ₃ CF ₃ , CF ₃ CHF ₂ and CClF ₂ CF ₃ as low-boiling portions are extracted from the top of the distillation column, CF ₃ CHClF and CF ₃ CH ₂ Cl as high boiling parts are extracted from the bottom of the column. The high boiling fraction extracted from the column bottoms circulates and reacts with hydrogen fluoride in step (1). Here, the total amount of the compound having a chlorine atom contained in the distilled material mainly containing CF ₃ CHF ₂ extracted from the upper portion of the column is preferably 0.02% by volume or less. The distillation material containing mainly CF ₃ CHF ₂ is used as a starting material in a direct fluorination reaction with fluorine gas.

The step (2) of the gas reaction mainly containing fluorine gas and CF ₃ CHF ₂ is described below.

Step (2) is carried out in the presence of a diluent gas, and the gas mainly containing CF ₃ CHF ₂ starts at a concentration lower than the explosion range. In particular, it is preferred that the CF ₃ CHF ₂ concentration at the reactor inlet be less than about 6 mol%. The diluting gas is a gas containing at least one selected from the group consisting of tetrafluoromethane, hexafluoroethane, octafluoropropane, and hydrogen fluoride, and is preferably a dilute gas rich in hydrogen fluoride.

The amount of fluorine gas used is preferably in the range of 0.5 to ₂ in the molar ratio of CF ₃ CHF ₂ (F ₂ / CF ₃ CHF ₂ ), preferably in the range of 0.9 to 1.3. The reaction temperature is in the range of 250 to 500 占 폚, preferably in the range of 350 to 450 占 폚. When the reaction temperature exceeds 500 ° C, the target CH ₃ CH ₃ is generated by CF _{4 and} is disadvantageously cleaved. When CClF ₂ CF ₃ is contained as an impurity, CClF ₃ is disadvantageously produced due to the cleavage of CClF ₂ CF ₃ On the other hand, if it is lower than 250 캜, the reaction proceeds slowly, which is not preferable.

The method of purifying the distilled gas from the reaction step of (2) is not particularly limited. The remainder of the unreacted fluorine gas can be removed, for example, by the addition of trifluoromethane as HCF, and then the residue is separated, for example, into hydrogen fluoride and organic matter. The separated hydrogen fluoride remains as a diluent gas in the direct fluorination reaction of step (2), but may also be used as a starting material in the fluorination reaction of (1). The composition of the separated organics is very different depending on the dilution gas used for the reaction, and the organic matter obtained from the use of hydrogen fluoride or a gas containing a large amount of the target gas CF ₃ CF ₃ contains CF ₃ CF ₃ as a main component . In the case of using tetrafluoroethane or octafluoroethane as the diluting gas, the gas is purified by performing distillation again. In either case, the high purity CF ₃ CF ₃ can be obtained by performing the distillation operation again according to the composition ratio of the obtained organic substance.

In distillation for the purification of organic matter, CF ₄ is extracted from the top of the first column, for example, as an inert gas and low-boiling fraction, and the gas mainly containing CF ₃ CF ₃ is extracted from the bottom of the column And introduced into the second distillation column. By then, trifluoroacetate as a portion, such as an inert gas and a low-cost methane is extracted from the top of the second distillation column, CF ₃ containing CF ₃ mainly gas is extracted from the column bottom, high purity CF ₃ CF ₃ are extracted from the top third distillation column The purification is carried out. The gas containing CClF ₂ CF ₃ collected from the bottom of the third distillate will be circulated to the reaction stage with the hydrogen fluoride of (1).

This pure CF ₃ CF ₃ contains almost no impurities, and high purity CF ₃ CF ₃ can be obtained. Its purity is 99.9997% by volume or more, the amount of the compound having chlorine atom is 1 volume ppm or less, and the amount of pentafluoroethane contained as impurities is 1 volume ppm or less.

CF ₃ CF _{3 having} a purity of 99.9997 vol% or more can be analyzed by gas chromatography (GC) or gas chromatography mass spectrometry (GC-MS) using TCD method, FID method ) Can be used.

Use of CF ₃ CF ₃ obtained by the production method of the present invention will be described below.

High purity CF ₃ CF ₃ can be used as the etching gas in the etching step of the semiconductor device manufacturing method and also as the cleaning gas in the cleaning step of the semiconductor manufacturing method.

In a semiconductor manufacturing method such as LSI and TFT, a thin film or a thick film is formed by CVD, sputtering, or vapor deposition, and the film is etched to form a circuit pattern. The apparatus for forming a thin film or a thick film is washed to remove unnecessary deposits accumulated on the inner wall of a jig device or the like because unnecessary deposits must be removed occasionally to cause generation of particles and to form a good film.

Etching method using CF ₃ CF ₃ may be performed under various dry etching conditions such as plasma etching, and microwave etching, CF ₃ CF ₃ are helium, nitrogen and argon, or a suitable ratio HCl, O _2, inert, such as H ₂ Gas and the like.

(Example)

The present invention will be described in more detail by way of the following Examples and Comparative Examples, but the present invention is not limited to these Examples.

Raw material example 1

In the presence of a fluorination catalyst tetrachlorethylene (CCl ₂ = CCl ₂₎ a reaction pressure of 0.4MPa, reaction temperature of 300 ℃ and 4 of HF / tetrachlorethylene to ethylene molar ratio was reacted with HF (first reaction), then the reaction Was further continuously reacted at a reaction pressure of 0.4 MPa, a reaction temperature of 330 ° C and a molar ratio of HF / intermediate (CF ₃ CHCl ₂ + CF ₃ CHClF) of ₄ (second reaction). After the reaction, the acid content was removed and the distillation operation was carried out by a conventional method. The distillate was analyzed by gas chromatography to find crude CF ₃ CHF ₂ (raw material 1 of CF ₃ CHF ₂ having the composition shown in Table 2 ).

compound Purity (% by volume) CF ₃ CHF ₂ 99.4513 CH ₃ Cl 0.0011 CHClF ₂ 0.0008 CHF ₃ 0.0224 CClF ₃ 0.0005 CF ₃ CClF ₂ 0.5216 CF ₃ CHClF 0.0008 CF ₃ CCl ₂ F 0.0009 CF ₃ CH ₂ Cl 0.0006

Raw material example 2

Was re-distilled material 1 of the CF ₃ CHF _2, obtained by the method in a conventional way, has shown the analysis of the distillate by gas chromatography to result in Table 3, the composition crude CF ₃ CHF ₂ (CF ₃ material of CHF ₂ 2 ).

compound Purity (% by volume) CF ₃ CHF ₂ 99.8000 CHClF ₂ 0.0002 CHF ₃ 0.0038 CF ₃ CClF ₂ 0.1960

Catalyst Example 1

A solution containing 452 g of Cr (NO ₃ ) ₃ .9H ₂ O dissolved in 1.2 L of pure water and 0.31 L of a 28% aqueous ammonia solution were added to a 10 L-volume vessel containing 0.6 L of pure water, Lt; / RTI > over about 1 hour with stirring under as much as possible. The resulting hydroxide slurry was filtered, cleaned with pure water, and then dried at 120 ° C. The solid thus obtained was ground, mixed with graphite, and then granulated with a tablet machine. The obtained particles were calcined in a nitrogen stream at 400 DEG C for 4 hours to obtain a catalyst precursor. This catalyst precursor was charged into a reactor made by Inconel and then subjected to a fluorination treatment (activation of the catalyst) in an HF atmosphere diluted with nitrogen at atmospheric pressure and at 350 ° C, and then the catalyst precursor was diluted with nitrogen in 100% Lt; RTI ID = 0.0 > 450 C < / RTI > under an HF atmosphere.

Catalyst Example 2

In a 10 L-volume container containing 0.6 L of pure water, 452 g of Cr (NO ₃ ) ₃ .9H ₂ O dissolved in 1.2 L of pure water and 42 g of In (NO ₃ ) ₃ .nH ₂ O (n is about 5) And 0.31 L of a 28% aqueous ammonia solution were added dropwise over about 1 hour under stirring to adjust the flow rates of the two aqueous solutions so as to be a reaction solution having a pH of 7.5 to 8.5. The resulting hydroxide slurry was filtered, washed thoroughly with pure water, and then dried at 120 DEG C for 12 hours. The solids thus obtained were milled and mixed with graphite and then granulated with a tablet machine. The obtained particles were calcined at 400 DEG C for 4 hours with nitrogen vapor to obtain a catalyst precursor. The catalyst precursor was filled in a reactor made by Inconel Co., and then a fluorination treatment (activation of the catalyst), which was the same method as that of Catalyst Example 1, was carried out.

(Example 1) Step (1)

150 ml of the catalyst prepared in [Catalyst Example 1] was charged into a 600-type reactor made by Inconel Co., Ltd., having an inner diameter of 1 inch and a length of 1 m, and the temperature was raised to 440 캜 while passing nitrogen gas. Hydrogen fluoride was supplied thereto at a rate of 3.5 NL / hr. Then, the raw material 1 of CF ₃ CHF ₂ obtained in [Example 1] was supplied at 3.5 NL / hr. The supply of nitrogen gas was stopped and the reaction started. After 2 hours, the exhaust gas was washed with an aqueous solution of potassium hydroxide to remove the acid content. After that, the gas composition was analyzed by gas chromatography to obtain a gas having the composition shown in Table 4.

compound Purity (% by volume) CF ₃ CHF ₂ 99.3273 CF ₄ 0.0113 CHF ₃ 0.0215 CF ₃ CF ₃ 0.6120 CF ₃ CClF ₂ 0.0156 CF ₃ CHClF 0.0112 CF ₃ CH ₂ Cl 0.0011

(Example 2) (1)

The reaction and analysis were carried out under the same conditions as in Example 1, except that the catalyst was filled with 150 m of the catalyst prepared in Catalyst Example 2. The results of the analysis are shown in Table 5.

compound Purity (% by volume) CF ₃ CHF ₂ 99.2732 CF ₄ 0.0170 CHF ₃ 0.0212 CF ₃ CF ₃ 0.6720 CF ₃ CClF ₂ 0.0068 CF ₃ CHClF 0.0098 CF ₃ CH ₂ Cl 0.0015

As is apparent from the analysis results shown in Table 5, when the fluorination catalyst obtained by adding indium to chromium was used, the conversion rate from CClF ₂ CF to CF ₃ CF ₃ was improved.

(Example 3) (1)

The reaction and analysis were carried out under the same conditions through the same procedure of Example 1 except that the reaction temperature was changed to 300 캜. The results of the analysis are shown in Table 6.

compound Purity (% by volume) CF ₃ CHF ₂ 99.4314 CF ₄ 0.0023 CHF ₃ 0.0221 CF ₃ CF ₃ 0.0387 CF ₃ CClF ₂ 0.4829 CF ₃ CHClF 0.0014 CF ₃ CH ₂ Cl 0.0005

(Example 4) Step (1)

The reaction and analysis were carried out under the same conditions through the same procedure as in Example 1 except that the reaction temperature was changed to 500 ° C. The results of the analysis are shown in Table 7.

compound Purity (% by volume) CF ₃ CHF ₂ 99.1948 CF ₄ 0.1488 CHF ₃ 0.0168 CF ₃ CF ₃ 0.5880 CHClF ₂ 0.0069 CF ₃ CClF ₂ 0.0148 CF ₃ CHClF 0.0256 CF ₃ CCl ₂ F 0.0021 CF ₃ CH ₂ Cl 0.0022

(Example 5) (1) Step + (2) Step

150 ml of the catalyst prepared in [Catalyst Example 2] was charged into a 600-type reactor made by Inconel Co., Ltd., having an inner diameter of 1 inch and a length of 2 m, and the temperature was raised to 430 캜 while passing nitrogen. Hydrogen fluoride was supplied thereto at 5.0 NL / hr, and the raw material 2 of CF ₃ CHF obtained in [Example 2] was supplied at 8.0 NR / hr. Subsequently, the supply of nitrogen gas was stopped and, after 2 hours from the start of the reaction, the solution was washed with an aqueous solution of potassium hydroxide to remove the acid content of the exhaust gas. The obtained gas composition was analyzed by gas chromatography, and as a result, a gas having the composition shown in Table 8 was obtained.

compound Purity (% by volume) CF ₃ CHF ₂ 99.7922 CF ₄ 0.0018 CHF ₃ 0.0036 CF ₃ CF ₃ 0.1980 CF ₃ CClF ₂ 0.0008 CF ₃ CHClF 0.0036

After removing the acid content, the gas having the composition shown in Table 8 was collected under cooling, and the distillate was purified according to the conventional method. The gas obtained after purification was analyzed, and the results are shown in Table 9.

compound Purity (% by volume) CF ₃ CHF ₂ 99.7950 CF ₄ 0.0019 CHF ₃ 0.0035 CF ₃ CF ₃ 0.1988 CF ₃ CClF ₂ 0.0008

As can be seen from the analysis results shown in Table 9, most of the chlorotetrafluoroethane can be removed by performing the distillation.

After the purification by the distillation obtained above, a direct fluorination reaction with fluorine gas was carried out using a gas mainly containing CF ₃ CHF ₂ .

A reactor of 600-type, manufactured by Inconel Co., Ltd., having an inner diameter of 20.6 mm and a length of 500 mm (using a heating method using an electric heater; the reactor was subjected to a passivation treatment with fluorine gas at a temperature of 500 ° C) Lt; RTI ID = 0.0 > 420 C. < / RTI >

Then, hydrogen fluoride was supplied at 50 NL / hr, and a gas mainly containing CF ₃ CHF ₂ was supplied at 3.5 NL / hr into one gas flow branched from the diluted gas. Thereafter, the fluorine gas was similarly fed into another gas flow branched from the diluting gas at 3.85 NL / hr to carry out the reaction. After 3 hours, the reaction product gas was washed with an aqueous potassium hydroxide solution and an aqueous potassium iodide solution to remove hydrogen fluoride and unreacted fluorine gas. The gas composition was then analyzed by gas chromatography. The results of the analysis are shown in Table 10.

compound Purity (% by volume) CF ₃ CHF ₂ 0.0001 CF ₄ 0.0456 CF ₃ CF ₃ 99.9536 CF ₃ CClF ₂ 0.0007

After removal of the acid content, the gas was collected under cooling and purified by distillation. After purification, the gas was analyzed by gas chromatography using TCD method, FID method, ECD method and GC-MS method, and the analysis results are shown in Table 11.

compound Purity (% by volume) CF ₃ CHF ₂ 0.9 vol ppm CF ₄ ≪ 0.4 volume ppm SF ₆ ≪ 0.4 volume ppm CF ₃ CClF ₂ ≪ 0.1 volume ppm CF ₃ CF ₂ 99.9998 vol%

11, CF ₃ CF ₃ after refining contains almost no other impurities, so that high purity CF ₃ CF ₃ was obtained, and its purity was more than 99.9997% by volume.

(Comparative Example 1)

A 600-type reactor (manufactured by Inconel Co., Ltd.) having an inner diameter of 20.6 mm and an inner diameter of 500 mm was heat-treated by a heater, and the reactor was passivated with fluorine gas at a temperature of 500 ° C. Lt; RTI ID = 0.0 > 420 C. < / RTI >

Then, hydrogen fluoride was supplied at 50 NL / hr, and raw material 1 of CF ₃ CHF ₂ obtained in [Material example 1] was supplied at 3.5 NL / hr into one gas flow branched from the dilution gas. Thereafter, the fluorine gas was similarly fed into another gas flow branched from the diluting gas at 3.85 NL / hr to carry out the reaction. After 3 hours, the reaction product gas was washed with an aqueous potassium hydroxide solution and an aqueous potassium iodide solution to remove hydrogen fluoride and unreacted fluorine gas. The gas composition was then analyzed by gas chromatography. The analysis results are shown in Table 12.

compound Purity (% by volume) CF ₃ CHF ₂ 0.0003 CF ₄ 0.0568 CClF ₃ 0.0036 CF ₃ CF ₃ 99.4160 CF ₃ CClF ₂ 0.5233

As apparent from the analysis results shown in Table 12, CF ₃ CHF ₂ containing a compound having a chlorine atom in the molecule as an impurity reacts with fluorine gas to generate CClF ₃ (chlorotrifluoromethane), which is difficult to separate do.

The gas having the composition shown in Table 12 after removal of the acid content was then collected under cooling and purified by distillation. The gas obtained after purification was analyzed, and the results are shown in Table 13.

compound Purity (% by volume) CF ₃ CHF ₂ 0.0003 CF ₄ <0.0001 CClF ₃ 0.0036 CF ₃ CF ₃ 99.9959 CF ₃ CClF ₂ <0.0001

As apparent from the analysis results shown in Table 13, CClF ₃ is a compound that is difficult to separate.

Above and to generate a high purity CF ₃ CF ₃ with a compound that holds the starting gas mixture, and chlorine gas containing CF ₃ CHF ₂ as described, according to the present invention, the resulting high purity CF ₃ CF ₃ A semiconductor device manufacturing process As an etching gas or a cleaning gas.

Claims (19)

(1) reacting a gas mixture containing pentafluoroethane and a compound having a chlorine atom with gaseous hydrogen fluoride in the presence of a fluorination catalyst to fluorinate the compound having the chlorine atom; And (2) reacting gaseous mixture containing pentafluoroethane and the fluorinated compound obtained in the step (1) with gaseous fluorine gas in the presence of a diluting gas . The method of claim 1, wherein the compound having a chlorine atom is selected from the group consisting of chloromethane, chlorotrifluoromethane, chloropentafluoroethane, dichlorotetrafluoroethane, chlorotetrafluoroethane, chlorotrifluoroethane, and chlorotri Fluoroethylene, and fluoroethylene. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt; The process for producing hexafluoroethane according to claim 1 or 2, wherein the total amount of the compound having a chlorine atom contained in the gas mixture in the step (1) is 1 vol% or less. The process for producing hexafluoroethane according to claim 1 or 2, wherein the total amount of the compound having a chlorine atom contained in the gas mixture in the step (1) is 0.5 volume% or less. The method for producing hexafluoroethane according to claim 1 or 2, wherein the fluorination catalyst in step (1) is a bulk catalyst obtained by adding indium to chromium oxide. The method for producing hexafluoroethane according to claim 1 or 2, wherein the temperature during the reaction with hydrogen fluoride in the presence of the fluorination catalyst in step (1) is in the range of 150 to 480 ° C. The process for producing hexafluoroethane according to claim 1 or 2, wherein the molar ratio of the hydrogen fluoride / organic substance contained in the gas mixture in the step (1) is in the range of 0.5 to 5. The process for producing hexafluoroethane according to claim 1 or 2, wherein the step of removing the acid content contained in the produced hydrogen chloride is carried out before the step (2). The process according to claim 1 or 2, wherein the step of separating the chlorotetrafluoroethane and / or the chlorotrifluoroethane and the step of separating the chlorotetrafluoroethane and / or the chlorotrifluoroethane into the step (1) Wherein the step of recovering the hexafluoroethane is carried out before the step (2). The process for producing hexafluoroethane according to claim 1 or 2, wherein the total amount of the compound having a chlorine atom contained in the gas mixture in the step (2) is 0.02% by volume or less. The process for producing hexafluoroethane according to claim 1 or 2, wherein the fluorinated compound contained in the gas mixture of step (2) is mainly composed of hexafluoroethane. The method according to claim 1 or 2, 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 Lt; RTI ID = 0.0 &gt; of hexafluoroethane. &Lt; / RTI &gt; The method for producing hexafluoroethane according to claim 1 or 2, wherein the diluent gas in step (2) is a gas rich in hydrogen fluoride. The method according to claim 1 or 2, wherein the temperature of the reaction of the gaseous mixture containing the fluorinated compound with the fluorine gas in the step (2) is in the range of 250 to 500 占 폚. Way. The method according to claim 1 or 2, wherein the temperature of the reaction of the fluorine compound with the gaseous mixture containing the fluorinated compound in the step (2) is in the range of 350 to 450 占 폚. Way. A hexafluoroethane product characterized by containing hexafluoroethane having a purity of at least 99.9997 vol%. The hexafluoroethane product according to claim 16, wherein the content of the compound having a chlorine atom is 1 ppm by volume or less and the content of pentafluoroethane is 1 ppm by volume or less An etching gas characterized by containing the hexafluoroethane product according to claim 16 or 17. A cleaning gas comprising the hexafluoroethane product according to claim 16 or 17.