JP2002087808A - Adsorbent for purifying perfluorocarbon, manufacturing method thereof, high purity octafluorocyclobutane, method of purifying and manufacturing the same and utilization thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorbent for purifying, which is for obtaining perfluorocarbon having impurity content controlled to <=1 mass-ppm by removing effectively the impurities contained in the perfluorocarbon, a manufacturing method thereof, high purity octafluorocyclobutane, a method of refining and manufacturing the same and a utilization thereof. SOLUTION: Perfluorocarbon is purified by using the adsorbent for purifying, which is manufactured using a method containing a process (1) for cleaning coal with an acid and washing, a process (2) for carrying out the deoxygenation and/or dehydration of the coal, a process for re-carbonizing the coal at 500-700 deg.C and a process (4) for activating the coal under a gaseous mixture flow containing an inert gas, carbon dioxide and steam in 700-900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an adsorbent for purifying perfluorocarbon, a method for producing the same, a high-purity octafluorocyclobutane, a method for purifying and producing the same, and uses thereof.

[0002]

2. Description of the Related Art Perfluorocarbon is used as an etching gas or a cleaning gas in a semiconductor device manufacturing process. For example, octafluorocyclobutane (hereinafter referred to as "FC-C318") is tetrafluoroethylene (hereinafter referred to as "FC-1114"). Alternatively, hexafluoropropene (hereinafter “FC-1216”)
That. ) In the production of FC
Obtained by purifying -C318. However, a method for producing FC-1114 or FC-1216 is described in, for example, chlorodifluoromethane (hereinafter referred to as “HCFC-2”) as described in EP451793.
2 ". ) Is a method of thermally decomposing, and there are many kinds of substances generated by the thermal decomposition reaction, and also contains many unreacted HCFC-22 and chlorine-containing compounds.

[0003]

[Table 1]

[0004] Table 1 shows the boiling points of FC-C318 and the compounds contained as impurities. Most of these reaction products and unreacted HCFC-22 can be separated by distillation. However, FC-1216, 2-chloro-
1,1,1,2-tetrafluoroethane (hereinafter referred to as “HCF
C-124 ". ), 1-chloro-1,1,2,2
-Tetrafluoroethane (hereinafter "HCFC-124a")
That. ), 1H-heptafluoropropane (hereinafter "H
FC-227ca ". ), 1,2-dichlorotetrafluoroethane (hereinafter referred to as “CFC-114”)
Has a boiling point close to that of FC-C318, and HCFC-12
4 and HCFC-124a form an azeotrope with FC-C318, so that the concentration of these impurities is 1 mass pp
It is very difficult to obtain FC-C318 of m or less by a purification method by distillation separation.

[0005] As a purification method other than the distillation separation, an extraction distillation method, a membrane separation method, an adsorption separation method and the like can be mentioned.
However, the extractive distillation method has problems such as high equipment costs and complicated processes, and the membrane separation method uses FC-C318.
There is no suitable membrane having characteristics necessary for separating impurities and impurities, and it is difficult to purify impurities to 1 mass ppm or less. Table 2 shows the molecular diameters (calculated values at the time of stable structure) of FC-C318 and impurity compounds. Existing adsorbents, for example, activated carbon, silica gel, zeolite (molecular sieve), molecular sieving carbon (hereinafter, referred to as molecular sieve) The adsorption separation method using “MSC”) has almost no difference in molecular diameter between FC-C318 and impurities, no difference in boiling point between FC-C318 and impurities, and furthermore, no difference between FC-C318 and impurities. Purification is difficult because of similarities in structure and properties.

[0006]

[Table 2]

Among them, activated carbon is one of the impurities, F
Although effective for adsorbing and removing C-1216, it is difficult to separate all other impurities. With the conventional purification method, it was particularly difficult to obtain FC-C318 in which the concentrations of HCFC-124 and HCFC-124a were 1 ppm by mass or less.

[0008]

SUMMARY OF THE INVENTION The present invention has been made under such a background, and the present invention relates to FC-1216, HCFC-1 contained in perfluorocarbon.
24, HCFC-124a, HFC-227ca, CF
It is an adsorbent for purification that can remove impurities such as C-114. In particular, it effectively removes HCFC-124 and HCFC-124a, which have been difficult to remove by conventional purification methods. It is an object of the present invention to provide an adsorbent for purification for obtaining a perfluorocarbon having a content of 1 mass ppm or less, a production method thereof, a high-purity octafluorocyclobutane, a purification method and a production method thereof, and a use thereof.

[0009]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have carried out acid cleaning treatment of raw coal to reduce metals, particularly alkali metals, in raw coal. The inventors have found that activated charcoal obtained by performing a series of activation treatments is an adsorbent having excellent characteristics for adsorbing the impurities contained in perfluorocarbon, and have completed the present invention. The present invention provides the following [1] to
[30].

[1] An adsorbent for purifying perfluorocarbon, which is produced by using a method including the following four steps. (1) Step of acid-cleaning and water-washing the raw coal (2) Deoxygenation and / or dehydration of the raw coal obtained in step (1) in an inert gas stream at a temperature range of 50 to 250 ° C. Step of performing (3) Step of recarburizing the raw coal obtained in Step (2) in a temperature range of 500 to 700 ° C. in an inert gas stream (4) Mixing containing inert gas, carbon dioxide and water vapor Step of activating the raw coal obtained in step (3) in a gas stream at a temperature in the range of 700 to 900 ° C. [2] The raw coal is selected from the group consisting of coconut shell coal, coal, charcoal, and tar pitch At least one is 400-60
The above [1] which has been carbonized in a temperature range of 0 ° C.
The adsorbent for purifying perfluorocarbon according to 1. [3] Purification of the perfluorocarbon according to the above [1] or [2], wherein the acid used in the acid washing treatment in the step (1) is a mineral acid, and the concentration of the acid is in the range of 1 to 1000 mol / m ^3. For adsorbent. [4] The acid used in the acid washing treatment in step (1) is hydrochloric acid and / or
The adsorbent for purifying perfluorocarbon according to any one of the above [1] to [3], which is sulfuric acid. [5] After the step (2), 300 to 5 in an inert gas stream.
The adsorbent for purifying perfluorocarbon according to any one of the above [1] to [4], wherein the step (3) is performed by raising the temperature to the recarbonization treatment temperature in the step (3) at a rate of 00 ° C./hr.

[6] After the step (3), the temperature is raised to the activation treatment temperature of the step (4) at a rate of 100 to 200 ° C./hr in an inert gas stream to carry out the step (4). ] ~
The adsorbent for purifying perfluorocarbon according to any one of [5]. [7] In the step (4), the mixed gas containing the inert gas, the carbon dioxide and the water vapor contains 50 to 8 inert gases.
The above [1] to which contain 9 vol%, 10 to 30 vol% of carbon dioxide, and 1 to 20 vol% of steam.
The adsorbent for purifying perfluorocarbon according to any one of [6]. [8] After the step (4), 200 to 3 in an inert gas stream.
The above [1] to cooling to room temperature at a rate of 00 ° C./hr
The adsorbent for purifying perfluorocarbon according to any one of [7]. [9] The adsorbent for purifying perfluorocarbon according to any one of the above [1] to [8], wherein the iodine adsorption amount is 700 to 1000 mg / g. [10] The adsorbent for purifying perfluorocarbon according to any one of the above [1] to [9], wherein the total content of alkali metals is 1000 ppm or less.

[11] The content of potassium is 500 ppm
The following adsorbent for purifying perfluorocarbon according to the above [10]. [12] The above-mentioned [1], wherein the perfluorocarbon is octafluorocyclobutane or octafluoropropane
The adsorbent for purifying perfluorocarbon according to any one of [11] to [11]. [13] A method for producing an adsorbent for purifying perfluorocarbon, comprising the following four steps. (1) Step of acid-cleaning and water-washing the raw coal (2) Deoxygenation and / or dehydration of the raw coal obtained in step (1) in an inert gas stream at a temperature range of 50 to 250 ° C. Step of performing (3) Step of recarburizing the raw coal obtained in Step (2) in a temperature range of 500 to 700 ° C. in an inert gas stream (4) Mixing containing inert gas, carbon dioxide and water vapor Step of activating the raw coal obtained in step (3) in a gas stream at a temperature in the range of 700 to 900 ° C. [14] The raw coal is selected from the group consisting of coconut shell coal, coal, charcoal, and tar pitch At least one is 400-6
The above [1] which has been carbonized in a temperature range of 00 ° C.
3] The method for producing an adsorbent for purifying perfluorocarbon according to 3). [15] Purification of the perfluorocarbon according to the above [13] or [14], wherein the acid used in the acid washing treatment in the step (1) is a mineral acid, and the concentration of the acid is in the range of 1 to 1000 mol / m ^3. Production method for adsorbents.

[16] The above-mentioned [13] to [1], wherein the acid used in the acid washing treatment in the step (1) is hydrochloric acid and / or sulfuric acid.
5] The method for producing an adsorbent for purifying perfluorocarbon according to any one of [5]. [17] After the step (2), 300 to 300
The production of the adsorbent for purifying perfluorocarbon according to any of the above [13] to [16], wherein the step (3) is carried out by raising the temperature to the recarbonization treatment temperature in the step (3) at a rate of 500 ° C./hr. Method. [18] After the step (3), 100 to 100 in an inert gas stream.
The method for producing a perfluorocarbon purification adsorbent according to any one of the above [13] to [17], wherein the step (4) is performed by raising the temperature to the activation treatment temperature in the step (4) at a rate of 200 ° C./hr. . [19] In the step (4), the mixed gas containing an inert gas, carbon dioxide, and water vapor has an inert gas of 50 to
The above [13] which contains 89 vol%, 10 to 30 vol% of carbon dioxide, and 1 to 20 vol% of steam.
The method for producing an adsorbent for purifying perfluorocarbon according to any one of [18] to [18]. [20] After the step (4), in an inert gas stream, 200 to
The above [13], which is cooled to room temperature at a rate of 300 ° C / hr.
The method for producing an adsorbent for purifying perfluorocarbon according to any one of [19] to [19].

[21] iodine adsorption amount of 700 to 1000
The method for producing an adsorbent for purifying perfluorocarbon according to any one of the above [13] to [20], which is mg / g. [22] The method for producing an adsorbent for purifying perfluorocarbon according to any one of the above [13] to [21], wherein the total content of alkali metals is 1000 ppm or less. [23] The method for producing an adsorbent for purifying perfluorocarbon according to the above [22], wherein the content of potassium is 500 ppm or less. [24] The above-mentioned [1], wherein the perfluorocarbon is octafluorocyclobutane or octafluoropropane
3] The method for producing an adsorbent for purifying perfluorocarbon according to any one of [23] to [23]. [25] Octafluorocyclobutane, which is obtained by bringing crude octafluorocyclobutane containing 10 to 10000 ppm of impurities into contact with the adsorbent for purifying perfluorocarbon according to any one of the above [1] to [12] and purifying it. Purification method.

[26] The impurity is 2-chloro-1,1,1,
1,2-tetrafluoroethane, 1-chloro-1,1,1
Octafluorocyclobutane according to the above [25], which is at least one compound selected from the group consisting of 2,2-tetrafluoroethane, 1,2-dichlorotetrafluoroethane, 1H-heptafluoropropane and hexafluoropropene Purification method. [27] A method for producing high-purity octafluorocyclobutane including the following steps (I) to (II). (I) Step of pyrolyzing chlorodifluoromethane to obtain crude octafluorocyclobutane (II) The crude octafluorocyclobutane obtained in step (I) is used for purifying the perfluorocarbon according to any one of claims 1 to 12. A step of purifying by contacting with an adsorbent [28] The purity of octafluorocyclobutane is 99.9
The method for producing octafluorocyclobutane according to the above [27], wherein the content is 999% by mass or more. [29] An etching gas containing octafluorocyclobutane having a purity of 99.9999% by mass or more. [30] A cleaning gas containing octafluorocyclobutane having a purity of 99.9999% by mass or more.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The adsorbent for purification of perfluorocarbon of the present invention,
It is manufactured using a method including the following four steps. (1) Step of acid-cleaning and water-washing the raw coal (2) Deoxygenation and / or dehydration of the raw coal obtained in step (1) in an inert gas stream at a temperature range of 50 to 250 ° C. Step of performing (3) Step of recarburizing the raw coal obtained in Step (2) in a temperature range of 500 to 700 ° C. in an inert gas stream (4) Mixing containing inert gas, carbon dioxide and water vapor Step of activating the raw coal obtained in step (3) in a gas stream at a temperature in the range of 700 to 900 ° C. The adsorbent for purifying perfluorocarbon of the present invention has a fine pore by performing the above-described processing step. It can be obtained as an adsorbent whose (micropore) diameter is controlled.

As the raw coal used for producing the adsorbent for purifying perfluorocarbon of the present invention, at least one selected from the group consisting of coconut shell coal, coal, charcoal and tar pitch can be used. Taking into account the denseness of charcoal required for pore development, hardness as an adsorbent, and the like, it is preferable to use coconut shell charcoal. Further, the carbonization temperature of the raw coal is not particularly limited, but the pores are hardly developed.
A carbonized product in the range of 00 to 600 ° C can be used, and a carbonized product in the range of 400 to 500 ° C is preferable.

Next, from the step (1) of subjecting the selected raw coal to an acid washing treatment and a water washing treatment, a step (2) of performing deoxygenation and / or dehydration, a step (3) of performing a recarbonization treatment, and activation. The processing steps up to the processing step (4) will be described. In the step (1), a step of performing an acid cleaning treatment and a water cleaning treatment,
This is a step performed to remove a metal component, particularly an alkali metal, contained in the raw coal. The metal component in the coking coal, particularly the alkali metal, acts as a catalyst in the activation treatment step (4), and promotes the reaction between the activation gas (steam and carbon dioxide) and the carbon atom in the coking coal. Control becomes difficult. Therefore, a washing step (1) with an acid and water is performed to remove metal components, particularly alkali metals.

As the acid used for the acid washing in the step (1), mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and organic acids such as acetic acid and trifluoroacetic acid can be used. Preferably a mineral acid is used, more preferably hydrochloric acid and / or
Alternatively, sulfuric acid is preferably used, and in view of the generated metal salt, hydrochloric acid is particularly preferably used. If the concentration of the acid is too low, the effect of removing the metal decreases, and if the concentration is too high, the effect becomes saturated.
³ , and preferably 200 to 500 mol /
m ³ is good. In addition, the ratio of the acid solution to the raw coal used in the acid washing is the same as the acid concentration, if it is too small, there is no effect, and if it is too large, it becomes saturated. And preferably 1:
It is better to be in the range of 1-2: 1.

The washing time may be about several hours if the washing temperature is high, and even if the temperature is as low as about room temperature, it may be left alone for about 24 hours, so that the metal contained in the raw coal can be sufficiently washed. Further, the water washing treatment performed after the acid washing is a washing for preventing the metal salt dissolved from the raw coal from being left in the raw coal, and the cleaning method is not particularly limited. For example, using water containing little metal salt such as tap water, continuous or batch washing can be sufficiently performed, and the completion of washing can be known by the pH (pH 3 to 5) of the washing liquid after washing.

The operation of drying the raw coal having been washed with water may be performed alone before the step (2), or may be performed in the step (2) of performing deoxidation and / or dehydration. Step (2)
Is a purge step of oxygen gas and moisture for reducing the influence of the oxygen source in the step (3) of performing the recarburizing treatment. Various inert gases can be used as the purge gas, and nitrogen gas is preferably used. Is good. The flow rate of the purge gas and the processing time are not particularly limited, and the gas flow rate and the processing time capable of smoothly exhausting the oxygen gas and moisture released from the raw coal outside the system can be appropriately selected. The temperature of the step (2) is also lower than the temperature of the re-carbonization treatment step (3), is constant, and does not re-carbonize for the purpose of promptly raising the temperature to the carbonization temperature in the step (3). A certain temperature range of 50 to 250 ° C. is preferable,
A temperature range of 00 to 250 ° C is good. Further, the adsorbent for purifying perfluorocarbon of the present invention comprises a process including steps (2) to (4) when using the above-mentioned raw coal washed at least by the method of step (1) as a starting material. Can be manufactured.

In the step (3) of performing the re-carbonization treatment, the raw coal from which the metal has been removed in the step (1) is subjected to heating to dry distillation to decompose tar components, develop and develop carbonized macropores, and carbonize the tar components. This is a step largely related to the development and development of pores in the activation treatment step (4). Therefore, it is necessary to pay attention to the temperature conditions in the step (3). First, as for the rate of temperature rise when the process (2) is shifted to the step (3), if the rate of temperature rise is low, tar components are not removed as dry distillation volatiles, and macropores do not tend to develop. The higher the heating rate, the better, but 300-500 ° C / hr
Can be selected from the range. Further, it is preferable that the heating is performed under an inert gas stream during the temperature rise.

If the temperature in the step (3) of performing the recarburizing treatment is low, volatile components cannot be sufficiently removed, the width of the pore distribution becomes wide, and if the temperature is high, the carbon substrate shrinks, and the micropores are reduced. Contraction occurs. Therefore, re-carbonization treatment is 500-700 ° C
Temperature, preferably from 600 to 70
The temperature range is preferably 0 ° C. The processing time for performing the re-carbonization may be 1 to 2 hours for the above purpose. In addition, the recarburizing process is performed in an inert gas stream, and various inert gases can be used as the inert gas.
Nitrogen gas is preferably used. The flow rate of the inert gas is
The rate is preferably 2 to 10 L / min, more preferably 3 to 5 L / min per 1 L of the raw coal.

The activation step (4) is a step of reacting the raw coal re-carbonized in the step (3) with the gas to develop pores, and the first step is to open closed pores in the crystal. The process proceeds in a second step, in which the walls between adjacent pores completely disappear and pores having a large diameter are formed.

In the step (4), it is necessary to pay attention to the conditions such as the composition of the gas to be treated, the temperature and the time. First, regarding the type of processing gas in the activation processing step (4), air (oxygen) is not preferable. The reason is that the reaction of the raw coal with the carbon is a reaction that generates a large amount of heat, so that it is difficult to control the temperature in the furnace and it is difficult to uniformly activate the furnace due to partial overheating. In addition, since the reaction of water vapor with carbon is relatively intense, it is difficult to control the pore diameter in the activation treatment step when used alone. For this reason, it is necessary to mix carbon dioxide and inert gas such as nitrogen, which reacts relatively slowly with water vapor with carbon, to form a gentle reaction. A contained mixed gas can be used.

The ratio of each component of the mixed gas is preferably such that the steam which violently reacts with the carbon is low, and is preferably a mixed gas composed of an inert gas, carbon dioxide and water vapor. 10 to 3 carbon dioxide
It is preferable to use one containing 0 vol% and 1 to 20 vol% of water vapor. More preferably, 70 to 80 nitrogen gas is used.
What contains vol%, carbon dioxide 15-25vol%, and steam 2-10vol% is good. The flow rate of the mixed gas is
The amount is preferably 0.5 to 3 L / min, more preferably 1 to 2 L / min per 1 L of the raw coal.

Since each of the steps (2) to (4) is carried out under heating, it is preferable to carry out the steps continuously, and in particular, the steps (3) and (4), which are processing steps at a higher temperature. Is preferably performed continuously. When the heating rate at the time of shifting from the step (3) to the step (4) is low, the closed pores in the carbon crystal body do not open and the surface area does not increase if the heating rate is low. Conversely, if the heating rate is high, the specific surface area and the pore size tend to be too large. Therefore, step (3)
From 100 to 200 ° C / hr from step (4)
It is preferable that

If the temperature in the activation treatment step (4) is low, the opening and expansion of the pores do not proceed sufficiently, and if the temperature is high, it is difficult to control the temperature. Therefore, the temperature of the activation process is 70
The temperature range is preferably from 0 to 900 ° C, preferably from 800 to 9 ° C.
00 ° C is good. When the treatment time is increased, the pore size of the activated carbon tends to increase due to the progress of the activation. Therefore, the treatment time can be determined by the size of the impurity to be removed by adsorption. For example, in order to adsorb impurities contained in FC-C318, which is one of the objects of the present invention, the treatment time can be selected from the range of 1 to 20 hours. Preferably, the processing time is between 5 and 18
Time is good.

After performing the step (4), the raw coal is cooled to room temperature under an inert gas stream, and the cooling rate is preferably as fast as possible. The temperature decreasing rate can be selected from the range of 200 to 300 ° C./hr. If the rate is low, it takes time for the temperature to decrease, and the adsorbent whose pore diameter is controlled tends to change pores, which is not preferable. . The flow rate of the inert gas is preferably large in order to smoothly remove the heat of the adsorbent out of the system, but can be selected from the range of 1.5 to 3 L / min per 1 L of the treated carbon.

By using the above-described method, the adsorbent for purifying perfluorocarbon of the present invention can be produced. The obtained adsorbent is obtained by subjecting the raw coal to acid washing and water washing. Particularly, it is characterized in that the content of alkali metal is small. The total content of alkali metals contained in the adsorbent is 1000 ppm or less, especially the content of potassium is 500 ppm or less, preferably 2 ppm or less.
It is not more than 00 ppm. As a method of measuring the content of the alkali metal in the adsorbent, for example, after the adsorbent is incinerated, it can be obtained by dissolving it in an acid and performing ICP measurement. The iodine adsorption amount is 700 to 1000 mg / g, and the method for measuring the iodine adsorption amount is JIS K1.
474. Further, the adsorbent for purifying perfluorocarbon of the present invention can be used as an adsorbent for purifying FC-C318 and FC-218 among perfluorocarbons, and the chlorine-based impurities contained in these perfluorocarbons are eliminated. It can be effectively adsorbed and removed.

Next, a method of purifying FC-C318 using the adsorbent produced by the above method will be described. As described above, in the FC-C 318, the HCF
C-124, HCFC-124a, CFC-114, H
At least one compound selected from the group consisting of FC227ca and FC-1216 is contained as an impurity, and the content of the impurity is usually in a range of 10 to 10,000 ppm. As a method for purifying FC-C318 of the present invention, a known method, for example, a flow method using a fixed bed can be used. The contact method using the flow method is preferably used because continuous treatment is possible. The contacting phase may be either a gas phase or a liquid phase, and the impurities can be effectively removed from the FC-C318.

The linear velocity of FC-C318 relative to the adsorbent is 1 to 10 m / min, preferably 2 to 5 m / min in the gas phase contact method. In the liquid phase contact method, it is 0.2 to 5 m / hr, preferably 0.5 to 2 m / hr.
hr. If the linear velocities of both the gaseous phase and the liquid phase are higher than the above, the adsorption band becomes longer and the time until breakthrough becomes shorter, so that the adsorption capacity tends to decrease.
In addition, even if it is small, there is no particular improvement in adsorption capacity,
On the contrary, it takes a long processing time, which is not preferable. Further, the treatment temperature for purification using the adsorbent of the present invention may be about room temperature, and in particular, cooling and heating need not be performed. The pressure may be a gauge pressure of 0 to 1 MPa, processing can be performed at a normal easy-to-handle pressure, and operations such as pressurization may not be performed.

The adsorbent can be regenerated and used when the adsorption capacity is satisfied. When regenerating the adsorbent, impurities including FC-C318 can be desorbed by passing the inert gas through the adsorbent at an elevated temperature, and nitrogen can be used as the inert gas. The regeneration temperature is preferably in the range of 100 to 400C, and more preferably, in the range of 100 to 200C.

As described above, high purity FC-C318 can be obtained by using the purification method of the present invention. Therefore, for example, in step (I), a step of thermally decomposing chlorodifluoromethane to obtain crude octafluorocyclobutane is performed, and in step (II), the crude octafluorocyclobutane obtained in step (I) is converted to By performing the step of contacting with a fluorocarbon purification adsorbent for purification, high-purity FC-C318 can be produced.

The content of impurities contained in FC-C318 is usually in the range of 10 to 10000 ppm, but the purity of FC-C318 obtained by using the production method of the present invention is 99.9999% by mass or more. . Here, FC-C
The purity of 318 is defined as a value obtained by subtracting halocarbon components other than FC-C318 from 100% by mass, and the method of analyzing FC-C318 having a purity of 99.9999% by mass or more includes (1) gas chromatography. (G
C) TCD method, FID method (all include the precut method), ECD method, and (2) analytical instruments such as gas chromatography-mass spectrometer (GC-MS) can be used.

The high-purity FC-C318 can be used as an etching gas in an etching step in a semiconductor device manufacturing process. Further, it can be used as a cleaning gas in a cleaning step in a semiconductor device manufacturing process. In a process for manufacturing a semiconductor device such as an LSI or a TFT, a thin film or a thick film is formed using a CVD method, a sputtering method, an evaporation method, or the like, and etching is performed to form a circuit pattern.
In an apparatus for forming a thin film or a thick film, cleaning is performed to remove unnecessary deposits deposited on an inner wall of the apparatus, a jig, and the like. This is because the generation of unnecessary deposits causes the generation of particles, and it is necessary to remove the deposits as needed in order to produce a high-quality film.

The etching method using FC-C318 can be performed under various dry etching conditions such as plasma etching and microwave etching.
-C318 and He, N _2, inert gas or HCl such as Ar, O _2, may be used by mixing in suitable proportions and gases such as H _2.

[0038]

EXAMPLES Hereinafter, 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. (Example 1) Coconut shell charcoal (from Philippines), which is coking coal
75 L was washed with hydrochloric acid having a concentration of 300 mol / m ³ , and then the water washing operation was repeated three times. 300 mol / m ³
The amount of hydrochloric acid used was the same volume as the raw coal to be washed. After adding hydrochloric acid to the raw coal, the mixture was allowed to stand for 15 hours and then drained. The amount of water at the time of washing was 5 times the volume of the raw coal, and completion of washing was confirmed by the fact that the pH of the washing solution after washing became 4.

Table 3 shows the results of analysis of the metal concentration in the raw coal before and after the acid washing.

[Table 3] As is clear from the measurement results of the metal content shown in Table 3, the acid content can reduce the metal content in the raw coal, and particularly, the alkali metal, which is an interfering substance for controlling the pore diameter, can be reduced. Of these, it was found that the potassium content could be significantly reduced.

Thereafter, the raw coal was burned in a firing furnace (electric external heat type metal rotary kiln: rotation speed set at 8 rpm, furnace inner diameter 950 m).
m, straight body 620 mm, 50 kw, 150 A (ma
x)) and dried under nitrogen at 90 ° C. for 2 hours. Nitrogen having a purity of 99% or more is used, and its flow rate is 50 L / min.
And Further, the dried raw coal was subjected to the processes of steps (2) to (4) in the above-described firing furnace under the conditions shown in Table 4.

[0041]

[Table 4]

Example 2 Inner diameter 11 mm × tower length 200 c
The adsorption tower of m was charged with 110 g of the adsorbent obtained by performing the activation treatment in the same manner as in Example 1. First, in order to remove moisture and volatile matter in the adsorbent, the adsorbent is kept at 120 ° C. for 2 hours and further for 150 hours before performing the adsorption treatment.
C. for 4 hours, for a total of 6 hours under a nitrogen stream (flow rate> 5 L /
min). To this adsorbent, add FC-1216 to 2
00 mass ppm, HCFC-124 and HCFC-124
a 50 ppm by mass, HFC-227ca 1
FC-C318 containing 00 mass ppm and 200 mass ppm of CFC-114 was brought into contact with the adsorbent in the gas phase under the conditions of room temperature, a pressure of 0.2 MPa, and a linear velocity of 2.5 m / min.
An impurity adsorption treatment was performed. The amount of impurities before and after treatment with the adsorbent was quantified by gas chromatography. The analysis conditions in gas chromatography-analysis are as follows.

Instrument body: GC-14B (manufactured by Shimadzu Corporation) Carrier: He gas Detector: Flame ionization detector (FID) Sample amount: 1 ml Quantitative method: simple area percentage (%)

Table 5 shows that 25, 50, 75, 100, and 125 hours after the start of distribution of FC-C318,
FC-1216 in FC-C318 at the outlet of the adsorption tower, H
CFC-124, HCFC-124a, HFC-227
The results of analysis of ca and CFC-114 were shown. It was found that the concentration of each substance was 1 ppm by mass or less after 125 hours. From these results, it was found that by bringing FC-C318 containing these impurities into contact with a series of activated adsorbents, the impurities could be adsorbed and separated, and high-purity FC-C318 could be obtained.

(Comparative Example 1) The same treatment as in Example 1 was carried out except that the acid washing and water washing steps of the coconut shell coal as the raw coal used in Example 1 were not performed, and the obtained adsorbent was used. In the same manner as in Example 2, an impurity adsorption treatment was performed. The amount of impurities before and after treatment with the adsorbent was similarly quantified by gas chromatography. Table 5 shows that the F-C at the outlet of the adsorption tower after 25 and 50 hours from the start of circulation of FC-C318.
FC-1216, HCFC-124 in C-C318,
HCFC-124a, HFC-227ca, CFC-1
The results of 14 analyzes are shown. As is clear from the results shown in Table 5, after 25 hours, the concentrations of all the substances exceeded 10 ppm by mass, and breakthrough was already seen,
It can be seen that the ability to adsorb impurities is clearly inferior to the adsorbent obtained by the method of Example 1. From this result, it was found that when the step of performing the acid washing treatment and the water washing treatment in the step of treating the raw coal was omitted, the pore diameter of the adsorbent was not controlled, and impurities were not absorbed and separated.

(Comparative Examples 2 and 3) Morsibon X2M4 /
6 (Comparative Example 2) as an adsorbent using 99 g (commonly known as MSC-5A, manufactured by Takeda Pharmaceutical Co., Ltd.) and 107 g of coconut shell activated carbon Y-10 (Comparative Example 3) (manufactured by Ajinomoto Fine Techno Co., Ltd.) An adsorption treatment of impurities was performed in the same manner as in Example 2 except that the adsorbent of Comparative Example 1 was used instead of the adsorbent. The amounts of impurities before and after the treatment with the activated carbon were similarly quantified by gas chromatography. In Table 5, as in Comparative Example 1, F
After 25 and 50 hours have passed since the start of circulation of C-C318, FC-121 in FC-C318 at the outlet of the adsorption tower was used.
6, HCFC-124, HCFC-124a, HFC-
The analysis results of 227ca and CFC-114 were shown. As a result, as in Comparative Example 1, after 25 hours, the concentrations of all the substances exceeded 10 ppm by mass, and breakthrough was already observed. As compared with the adsorbent obtained by the method of Example 1, the adsorbing ability of the impurities was clearly inferior, and it was found that, similarly to Comparative Example 1, the impurities were not sufficiently adsorbed and separated.

[0047]

[Table 5]

Further, the adsorption capacities of the respective impurities with respect to the respective adsorbents used in Example 2 and Comparative Examples 1 to 3 were measured, and the results are shown in Table 6. The impurity adsorption capacity is determined as the breakthrough point where the concentration of each impurity in the gas at the outlet of the adsorption tower exceeds 1 mass ppm, and the adsorption amount of each impurity up to that point is determined. It was calculated by dividing by the weight of the agent. Comparing the results of Example 2 and Comparative Examples 1 to 3,
It was found that the adsorption capacity of impurities of the adsorbent used in Example 2 was remarkably improved as compared with that of Comparative Example.

[0049]

[Table 6]

Example 3 101 g of an adsorbent obtained by performing the activation treatment in the same manner as in Example 1 was packed in an adsorption tower having an inner diameter of 22 mm and a tower length of 60 cm.
It was used after being treated in a helium stream for 2 hours at 150 ° C. for 4 hours. Using this adsorbent, FC-C318 containing 450-12 ppm by mass of only FC-1216 was passed through the adsorbent in the gas phase under the conditions of room temperature, 0.2 MPa, and a linear velocity of 4 m / min. The amount of impurities before and after treatment with the adsorbent,
It was similarly quantified by gas chromatography. Similarly, the breakthrough point of the adsorbent was determined, and the adsorption capacity of FC-1216 was calculated. Table 7 shows the results.

(Comparative Examples 4 to 6) 104 g of the same activated carbon Y-10 as in Comparative Example 3 (Comparative Example 4), and granular activated carbon C
L-H was 94 g (manufactured by Ajinomoto Fine Techno Co., Ltd.) (Comparative Example 5), and 91 g (Comparative Example 6) of MSC-5A similar to Comparative Example 2 was used as the adsorbent. FC-1216 as in Example 3 except that it was used instead.
Was adsorbed. The amount of impurities before and after treatment with the adsorbent was similarly quantified by gas chromatography. As in Example 3, the adsorption capacity of FC-1216 was calculated, and the results are shown in Table 7.

[0052]

[Table 7] From the results of Example 3 and Comparative Examples 4 to 6, FC
Although the adsorption with -1216 alone was certainly effective in the conventional activated carbon system, the adsorption capacity of the adsorbent of the present invention is remarkably improved such as showing about 10 times the amount of the conventional activated carbon. It was found to be more effective than the adsorbent.

[0053]

As described above, by using the adsorbent for purifying perfluorocarbon of the present invention, high purity FC can be obtained.
-C318 can be obtained, and high-purity FC-C318 manufactured using the present invention can be used as an etching gas or a cleaning gas in a semiconductor device manufacturing process.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C10B 53/02 C10B 53/02 F term (Reference) 4G046 HA01 HA02 HA05 HA07 HB02 HC09 HC10 4G066 AA04B AA10D AA14D AA34D AA43D AA47D AC06A AC08A BA36 CA33 DA05 FA11 FA18 FA21 FA23 FA33 FA34 FA37 FA40 4H006 AA02 AD17 EA02 4H012 JA03

Claims (30)

[Claims] 1. An adsorbent for purifying perfluorocarbon, which is produced by using a method comprising the following four steps. (1) Step of acid-cleaning and water-washing the raw coal (2) Deoxygenation and / or dehydration of the raw coal obtained in step (1) in an inert gas stream at a temperature range of 50 to 250 ° C. Step of performing (3) Step of recarburizing the raw coal obtained in Step (2) in a temperature range of 500 to 700 ° C. in an inert gas stream (4) Mixing containing inert gas, carbon dioxide and water vapor A step of activating the raw coal obtained in step (3) in a gas stream at a temperature in the range of 700 to 900 ° C. 2. The raw material coal is at least one selected from the group consisting of coconut shell coal, coal, charcoal, and tar pitch.
The adsorbent for purifying perfluorocarbon according to claim 1, which has been carbonized in a temperature range of 0 to 600 ° C. 3. The purification method for perfluorocarbon according to claim 1, wherein the acid used in the acid washing treatment in the step (1) is a mineral acid, and the concentration of the acid is in the range of 1 to 1000 mol / m ³ . Sorbent. 4. The adsorbent for purifying perfluorocarbon according to claim 1, wherein the acid used in the acid washing treatment in the step (1) is hydrochloric acid and / or sulfuric acid. 5. After the step (2), the reaction is carried out in a stream of inert gas.
The adsorbent for purifying perfluorocarbon according to any one of claims 1 to 4, wherein the step (3) is performed by raising the temperature to the recarbonization treatment temperature in the step (3) at a rate of 00 to 500 ° C / hr. 6. After the step (3), 1 hour in a stream of inert gas.
The adsorbent for purifying perfluorocarbon according to any one of claims 1 to 5, wherein the step (4) is performed by raising the temperature to the activation treatment temperature in the step (4) at a rate of 00 to 200 ° C / hr. 7. In the step (4), the mixed gas containing an inert gas, carbon dioxide and water vapor contains 50 to 89 vol% of inert gas and 10 to 30 vol% of carbon dioxide.
%, And an adsorbent for purifying perfluorocarbon according to any one of claims 1 to 6, which contains 1 to 20 vol% of water vapor. 8. After the step (4), the reaction is carried out in a stream of inert gas.
The adsorbent for purifying perfluorocarbon according to any one of claims 1 to 7, wherein the adsorbent is cooled to room temperature at a rate of 00 to 300 ° C / hr. 9. An iodine adsorption amount of 700 to 1000 mg /
The adsorbent for purifying perfluorocarbon according to any one of claims 1 to 8, which is g. 10. The total alkali metal content is 1000 p.
pm or less, The adsorbent for purifying perfluorocarbon according to any one of claims 1 to 9. 11. The adsorbent for purifying perfluorocarbon according to claim 10, wherein the content of potassium is 500 ppm or less. 12. The adsorbent for purifying perfluorocarbon according to claim 1, wherein the perfluorocarbon is octafluoropropane or octafluorocyclobutane. 13. A method for producing an adsorbent for purifying perfluorocarbon, comprising the following four steps. (1) Step of acid-cleaning and water-washing the raw coal (2) Deoxygenation and / or dehydration of the raw coal obtained in step (1) in an inert gas stream at a temperature range of 50 to 250 ° C. Step of performing (3) Step of recarburizing the raw coal obtained in Step (2) in a temperature range of 500 to 700 ° C. in an inert gas stream (4) Mixing containing inert gas, carbon dioxide and water vapor A step of activating the raw coal obtained in step (3) in a gas stream at a temperature in the range of 700 to 900 ° C. 14. The raw coal is at least one selected from the group consisting of coconut shell charcoal, coal, charcoal and tar pitch.
The method for producing an adsorbent for purifying perfluorocarbon according to claim 13, which has been carbonized in a temperature range of 00 to 600 ° C. 15. The method for purifying a perfluorocarbon according to claim 13, wherein the acid used in the acid washing treatment in the step (1) is a mineral acid, and the concentration of the acid is in the range of 1 to 1000 mol / m ³ . Method for producing adsorbent. 16. The method for producing an adsorbent for purifying perfluorocarbon according to claim 13, wherein the acid used in the acid washing treatment in step (1) is hydrochloric acid and / or sulfuric acid. 17. The method according to claim 13, wherein after the step (2), the step (3) is carried out in an inert gas stream at a rate of 300 to 500 ° C./hr up to the recarburizing treatment temperature of the step (3). ~ 16
The method for producing an adsorbent for purifying perfluorocarbon according to any one of the above. 18. The method according to claim 13, wherein after the step (3), the step (4) is performed by raising the temperature to the activation treatment temperature of the step (4) at a rate of 100 to 200 ° C./hr in an inert gas stream. 18. The method for producing an adsorbent for purifying perfluorocarbon according to any one of 17. 19. In the step (4), the mixed gas containing an inert gas, carbon dioxide and water vapor contains 50 to 89 vol% of inert gas and 10 to 30 vol% of carbon dioxide.
The method for producing an adsorbent for purifying perfluorocarbon according to any one of claims 13 to 18, comprising 1 to 20% by volume of water vapor. 20. The adsorbent for purifying perfluorocarbon according to any one of claims 13 to 19, wherein, after the step (4), the adsorbent for purifying perfluorocarbon is cooled to room temperature in an inert gas stream at a rate of 200 to 300 ° C./hr. Production method. 21. An iodine adsorption amount of 700 to 1000 mg
The method for producing an adsorbent for purifying perfluorocarbon according to any one of claims 13 to 20, which is / g. 22. The total alkali metal content is 1000 p
22. The method for producing an adsorbent for purifying perfluorocarbon according to any one of claims 13 to 21, which is not more than pm. 23. The method for producing an adsorbent for purifying perfluorocarbon according to claim 22, wherein the content of potassium is 500 ppm or less. 24. The method for producing an adsorbent for purifying perfluorocarbon according to any one of claims 13 to 23, wherein the perfluorocarbon is octafluoropropane or octafluorocyclobutane. 25. Octafluorocyclobutane obtained by contacting crude octafluorocyclobutane containing 10 to 10000 ppm of impurities with the adsorbent for purifying perfluorocarbon according to any one of claims 1 to 12. Purification method. 26. The method according to claim 26, wherein the impurity is 2-chloro-1,1,1,1.
2-tetrafluoroethane, 1-chloro-1,1,2,2
The method for purifying octafluorocyclobutane according to claim 25, which is at least one compound selected from the group consisting of 2-tetrafluoroethane, 1,2-dichlorotetrafluoroethane, 1H-heptafluoropropane, and hexafluoropropene. 27. A method for producing high-purity octafluorocyclobutane, comprising the following steps (I) to (II). (I) Step of pyrolyzing chlorodifluoromethane to obtain crude octafluorocyclobutane (II) The crude octafluorocyclobutane obtained in step (I) is used for purifying the perfluorocarbon according to any one of claims 1 to 12. Step of purification by contact with adsorbent 28. The method for producing octafluorocyclobutane according to claim 27, wherein the purity of octafluorocyclobutane is 99.9999% by mass or more. 29. An etching gas containing octafluorocyclobutane having a purity of 99.9999% by mass or more. 30. A cleaning gas containing octafluorocyclobutane having a purity of 99.9999% by mass or more.