JP6777852B2 - Fluorine-containing compound gas detection method - Google Patents

Description

The present invention relates to a method for detecting a fluorine-containing compound gas capable of detecting a trace amount of the fluorine-containing compound gas.

Many fluorocarbon compound gases such as chlorofluorocarbons, perfluorocarbons, and perfluorocompounds have high ozone depletion potential (ODP) and global warming potential (GWP), which has become a major international problem in recent years. It has become. For this reason, alternative gases with low ODP and GWP have been developed, but many of them are flammable or toxic.

For the detection of these fluorine-containing compound gases, there are infrared type sensors that utilize the infrared absorption of the fluorine-containing compound gas and heat ray type sensors that utilize the resistance change of the heat ray coil, but the lower limit of detection is several hundred ppm in both cases. It was impossible to detect a few ppm of fluorine-containing compound gas. The alternative gases with low ODP and GWP that have been developed in recent years include many flammable or toxic gases, and it is necessary to detect a trace amount of these gases on the order of several ppm.

As a method for detecting a trace amount of fluorine-containing compound gas on the order of several ppm, the applicant applies a contact reaction with a heated solid metal to convert the gas into a gas that is easy to detect, and the gas is detected by gas detection using electrolysis. A method for detecting a fluorine-containing compound gas, which is characterized by detecting by the output of a gas detector or a tape-type gas detector, has been disclosed (Patent Document 1). Further, as a method for obtaining the required reaction rate even when the reaction temperature is further lowered, a method using the solid metal in which an alkali metal fluoride is impregnated on the surface has been proposed (Patent Document 2). Then, as a method of uniformly holding the adhering material on the surface for a long period of time, it has been proposed to use the adhering material as an alkali metal hydroxide or a metal oxide (Patent Document 3).

Japanese Patent No. 3375072 Japanese Patent No. 3460601 Japanese Unexamined Patent Publication No. 2003-139760

However, in the method for detecting a fluorine-containing compound gas, when the solid drug in which an alkali metal fluoride or the like is impregnated with a solid metal is used, the required reaction rate can be obtained even if the reaction temperature is lowered, but the temperature is 400 ° C. High temperature heating is required (Patent Documents 2 and 3). Therefore, the heating device becomes large, and the material of the heating device is also limited to those that can withstand this temperature. In addition, the running cost also increases because the power consumption increases. The present invention has been made focusing on such a point, and an object of the present invention is to provide a method capable of detecting a trace amount of a fluorine-containing compound gas even when the heating temperature for causing a reaction is lowered.

As a result of diligent studies on the above-mentioned problems, the present inventor causes a reaction for detecting a trace amount of fluorine-containing compound gas by reacting the fluorine-containing compound gas with a solid metal oxide instead of a solid metal. It has been found that the heating temperature for the compound is lowered. Furthermore, they have found that it is effective to impregnate an alkali metal fluoride or an alkali metal oxide on the surface of the metal oxide in the reaction, and have reached the present invention.

That is, the present invention provides a method for detecting a fluorine-containing compound gas, which comprises contacting a fluorine-containing compound gas and a solid metal oxide in a temperature range of 100 to 800 ° C. to detect the generated gas. ..

The present invention can provide a method capable of detecting a trace amount of a fluorine-containing compound gas even at a heating temperature lower than that of the prior art.

It is the schematic of the experimental apparatus for the detection confirmation of a fluorine-containing compound gas.

Hereinafter, the present invention will be described in detail.
In the method for detecting a fluorine-containing compound gas of the present invention, a solid metal oxide or a substance in which an alkali metal oxide or an alkali metal fluoride is impregnated therein is mixed with a gas containing a trace amount of the fluorine-containing compound gas at 100 to 800 ° C. It is characterized by including a step of making a contact reaction in a temperature range and a step of detecting a gas generated by the reaction.

The fluorine-containing compound gas to be detected is chlorofluorocarbon, perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, perfluorocompound, etc., and in particular, C ₅ F ₈ , C ₄ F ₈ , C ₄ F ₆ , C ₂ F ₆ , C ₃ F ₈ , CF ₄ , C ₅ HF ₇ , CH ₂ F ₂ , CHF ₃ , CCl ₃ F, CCl ₂ F ₂ , CCl F ₃ , CCl ₄ , CHClF ₂ , CH ₃ Cl, CH _{3 Br, CHCl 3, CBr 2 F} 2, CBrF 3, CH 2 Br 2, CH 2 BrCl, CBr 3 F, CHBr 2 F, CHBrF 2, CBrClF 2, C 2 H 3 Cl, C 2 BrF 5, C 2 ClF ₅ , C ₂ Cl ₂ F ₄ , C ₂ Cl ₃ F ₃ , C ₂ BrF ₄ , C ₂ Br ₂ F ₄ , C ₂ H ₂ Br ₂ F ₄ , C ₂ Br ₂ ClF ₃ , NF ₃ . Regarding the gas targeted by the detection method of the present invention, the trace amount is a gas having a concentration of fluorine-containing compound gas of several thousand volume ppm or less, and particularly a gas having a concentration range of 1 ppb or more and 1000 ppm or less. In particular, when C ₅ F ₈ is the target of detection, since the permissible exposure concentration is 2 volume ppm, it is preferable that it can be detected well in the concentration range of 0.01 volume ppm or more and 20 volume ppm or less, and 0.1 volume. It is more preferable that it can be detected well in the concentration range of ppm or more and 10 volumes by ppm or less.

In the present invention, the above-mentioned fluorine-containing compound gas and a solid metal oxide are contact-reacted under a heated state to be converted into a gas such as SiF ₄ or WF ₆ , which is a gas that is easier to detect. The surface of the solid metal oxide may be impregnated with alkali metal fluoride or alkali metal hydroxide.

The solid metal oxide used in the present invention is at least one selected from the group consisting of silicon oxide and tungsten oxide. SiO ₂ is an example of the silicon oxide, and WO ₃ is an example of the tungsten oxide. be able to. As the adhering material, the alkali metal fluoride is sodium fluoride or potassium fluoride or the like, and the alkali metal hydroxide is sodium hydroxide or potassium hydroxide or the like. By impregnating them, the solid metal oxide reacts with the fluorine-containing compound gas at a lower temperature.

In the present invention, the outer shape of the solid metal oxide is spherical or crushed. The surface state is not particularly limited, but a porous one having a large surface area or a roughened one is desirable. The purity of the solid metal oxide is not particularly limited, but is preferably 90% by mass or more, more preferably 98% by mass or more, and further preferably 99% by mass or more.

The size of the solid metal oxide is such that it has passed through a sieve having a mesh size of 9.5 mm and has not passed through a sieve having a mesh size of 0.5 mm. Larger ones that do not pass through a sieve with a mesh size of 9.5 mm have problems such as a large filling space, a large amount of gas to be detected, and a decrease in the contact area with the gas, resulting in insufficient reaction. Therefore it is not suitable. Further, the one that has passed through a sieve having an opening of 0.5 mm is not suitable because it blocks the path of the gas to be measured and obstructs the flow.

Using C ₅ F ₈ gas in the fluorine-containing compound gas, at 280 ± 50 ° C. In the presence of oxygen when contacted with SiO ₂ is a solid metal oxide, (1) if the detected easily measured gas, such as type A certain SiF ₄ is obtained. Similar reactions are believed to occur in the temperature range of 100-800 ° C.
_{C 5 F 8 + 2SiO 2 +} 3O 2 → 2SiF 4 + 5CO 2 (1)

When an alkali metal hydroxide is used as an adjunct, the alkali metal hydroxides such as NaOH and KOH form various metal fluorides by reacting with a fluorine-containing compound gas. For example, using the C ₅ F ₈ gas in the fluorine-containing compound gas, the use of NaOH in the alkali metal oxides, at 300 ± 50 ° C. in the presence of oxygen (2) reactions such as is obtained.
C ₅ F ₈ + ₈ NaOH + 3O ₂ → 8NaF + 4H ₂ O + 5CO ₂ (2)
In the NaF produced here, when SiO ₂ is used as the solid metal oxide, SiF ₄ is produced at 300 ± 50 ° C. as shown in the equation (3) in the presence of water.
4NaF + SiO ₂ + 2H ₂ O → SiF ₄ + 4NaOH (3)

When alkali metal fluoride is used as an adjunct, treatment is required in advance. For example, when NaF is used as the alkali metal fluoride and SiO ₂ is used as the solid metal oxide, SiF ₄ is produced at 300 ± 50 ° C. as shown in the formula (3) in the presence of water and oxygen. To. NaF is replaced with NaOH with the formation of SiF ₄ , and it is necessary to separately discharge SiF ₄ to the outside of the system until this is completed. After the replacement, detection of fluorine-containing compound gas is performed from (2) to (3). ) The reaction mechanism is the same as the equation. As described _above, in processing the C 5 _{F 8} gas, a solid metal oxide 200 to 500 ° C., preferably 250 to 400 ° C., it is preferably heated and more preferably to 300 to 380 ° C..

FIG. 1 shows a schematic view of an experimental device for detecting and confirming a fluorine-containing compound gas according to the method of the present invention. The sample gas filling container 1 is filled with a gas containing a trace amount of fluorine-containing compound to be detected in the atmosphere. The filling cylinder 2 is filled with a solid metal oxide, a solid metal, or an alkali metal fluoride or an alkali metal hydroxide impregnated therein, and the gas in the sample gas filling container is filled in the filling cylinder at 500 cm / min. Introduce about ³ and bring it into contact with the filling. The filling cylinder 2 is heated by the heating heater 3 to heat the filling inside the filling cylinder. However, since the heating temperature drops due to the flow of gas, a temperature higher than the above-mentioned reaction temperature is required to confirm the detection of the fluorine-containing compound gas. From the outlet of the filling cylinder 2, the gas detector 4 using electrolysis and the tape type gas detector 5 are introduced, and these gas detectors obtain the electric output required for detection.

In the gas detector 4 using electrolysis, gas such as SiF ₄ and WF ₆ can be electrolyzed on the electrode, and the fluorine-containing compound gas can be detected by the electric output generated at that time. Further, in the tape type gas detector 5, which is another type of gas detector, gas such as SiF ₄ and WF ₆ is applied to a breathable tape made of a material such as nitrocellulose impregnated with a color former. It is passed and the reflected light from the color developed by the reaction is converted into an electric output, and the fluorine-containing compound gas is detected.

Hereinafter, description will be made in detail with reference to Examples, but the present invention is not limited to such Examples. In addition, Examples and Comparative Examples are summarized in Tables 1 and 2.

[Example 1]
Atmosphere of C ₅ F ₈ = 10 volume ppm was used as the gas to be detected, and spherical porous SiO ₂ was used as the solid metal oxide. The size of the solid metal oxide is such that it has passed through a sieve having a mesh size of 2.0 mm and has not passed through a sieve having a mesh size of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C.
After introducing the gas to be detected, detection was confirmed by the gas detector using electrolysis and the tape type gas detector by the component of the gas generated by the reaction with the solid metal oxide as shown in Table 1 (Table 1). (Indicated by ○).

[Examples 2-35]
The measurement was carried out by changing the detection target gas in the same manner as in Example 1. The concentration of the detection target gas was 10 volumes ppm in the atmosphere. As shown in Table 1, the measurement results for each detection target gas were confirmed to be detected by the gas detector using electrolysis and the tape type gas detector even if the type of the detection target gas was changed.

[Example 36]
The measurement was carried out by using a spherical porous WO ₃ instead of SiO _{2 as} the metal solid oxide in the same manner as in Example 1. As a result, even if the type of metal oxide was changed as shown in Table 1, detection was confirmed by the gas detector using electrolysis and the tape type gas detector.

[Examples 37-40]
In the same manner as in Example 1, alkali metal fluorides NaOH and KF and alkali metal hydroxides NaOH and KOH were used as adhering substances on the surface of the solid metal oxide, and the SiO ₂ was added by weight. The measurement was carried out by adhering to 1000 ppm. The filling cylinder heating temperature was 330 ° C. As shown in Table 1, the measurement results by the attachments were confirmed by the gas detector using electrolysis and the tape type gas detector.

[Comparative Example 1]
In the same manner as in Example 1, Si, which is a solid metal, was used instead of SiO ₂ , which is a solid metal oxide. The size of the solid metal is such that it has passed through a sieve having a mesh size of 2.0 mm and has not passed through a sieve having a mesh size of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C. in the same manner as in Example 1.
After the introduction of the gas to be detected, detection was not confirmed in the gas detector using electrolysis and the tape type gas detector due to the components of the gas generated by the reaction with the solid metal as shown in Table 2 (in Table 2). (Indicated by x).

[Comparative Examples 2-3]
The measurement was carried out using the same method as in Comparative Example 1 with the detection target gases being C ₄ F ₆ and C ₅ HF ₇ . The concentration of the detection target gas was 10 volumes ppm in the atmosphere. The heating temperature of the filling cylinder was 350 ° C. as in Examples 3 and 7. As shown in Table 1, the measurement results for each detection target gas were not confirmed by the gas detector using electrolysis and the tape type gas detector even if the type of the detection target gas was changed.

[Comparative Example 4]
In the same manner as in Comparative Example 1, W was used instead of Si, which is a solid metal. The size of the solid metal is such that it has passed through a sieve having a mesh size of 2.0 mm and has not passed through a sieve having a mesh size of 1.0 mm. These were filled in a filling cylinder and heated to 350 ° C. in the same manner as in Example 35.
After the introduction of the gas to be detected, detection was not confirmed in the gas detector using electrolysis and the tape type gas detector due to the components of the gas generated by the reaction with the solid metal as shown in Table 1 (in Table 2). (Indicated by x).

[Comparative Examples 5 to 6]
In the same manner as in Comparative Example 1, NaF, which is an alkali metal fluoride, and NaOH, which is an alkali metal hydroxide, are used as adhering substances on the surface of the solid metal, and the Si is impregnated so as to have a weight ratio of 1000 ppm. , The measurement was carried out. The filling cylinder heating temperature was set to 330 ° C. as in Examples 37 to 40. As shown in Table 1, the measurement results for each of the attachments were not confirmed by the gas detector using electrolysis and the tape type gas detector.

Comparing Example 1 and Comparative Example 1, in the detection of the same fluorine-containing compound gas, the solid metal in the filling cylinder that reacts with the gas is a solid metal oxide, which is necessary for the detection of the gas. The heating temperature of the filling cylinder could be lowered. It is considered that this is because the gas or the gas generated from the gas has a higher reaction rate with the solid metal oxide than the solid metal, and the heating temperature can be lowered.
As described in detail above, according to the method of the present invention, in the method for detecting a fluorine-containing compound gas, a gas containing a trace amount of the fluorine-containing compound gas is contact-reacted with a heated solid metal oxide to detect the generated gas. Therefore, it can be detected at a low heating temperature.

According to the present invention, for example, when a fluorine-containing compound gas used in a semiconductor device manufacturing process leaks from an apparatus or is mixed with an outlet gas of an exhaust gas treatment apparatus, even a trace amount of the fluorine-containing compound gas can be detected. It is possible to prevent the exposure of gas to workers and the release into the atmosphere.

1 ... Sample gas (fluorine-containing compound gas) filling container 2 ... Filling cylinder 3 ... Filling cylinder Heater 4 ... Gas detector using electrolysis 5 ... Tape type gas detector

Claims (8)

It is characterized in that a fluorine-containing compound gas and a solid metal oxide are contact-reacted in a temperature range of 100 to 800 ° C., and the generated gas is detected .
The fluorine-containing compound gas is C ₅ F ₈ , C ₄ F ₈ , C ₄ F ₆ , C ₂ F ₆ , C ₃ F ₈ , CF ₄ , C ₅ HF ₇ , CH ₂ F ₂ , CHF ₃ , CCl ₃ F, CCl ₂ F ₂ , CClF ₃ , CHClF ₂ , CBr ₂ F ₂ , CBrF ₃ , CBr ₃ F, CHBr ₂ F, CHBrF ₂ , CBrClF ₂ , C ₂ BrF ₅ , C ₂ ClF ₅ , C ₂ Cl ₂ F One or more selected from the group consisting of ₄ , C ₂ Cl ₃ F ₃ , C ₂ BrF ₄ , C ₂ Br ₂ F ₄ , C ₂ H ₂ Br ₂ F ₄ , C ₂ Br ₂ ClF ₃ , and NF ₃ . ,
The solid metal oxide is at least one selected from the group consisting of silicon oxide and tungsten oxide.
A method for detecting a fluorine-containing compound gas in which the concentration of the fluorine-containing gas is in the concentration range of 1 volume ppb or more and 1000 volume ppm or less . The method for detecting a fluorine-containing compound gas according to claim 1 , wherein the silicon oxide is SiO ₂ and the tungsten oxide is WO ₃ . The method for detecting a fluorine-containing compound gas according to claim 1 or 2 , wherein at least one selected from the group consisting of alkali metal fluoride and alkali metal hydroxide is impregnated on the surface of the solid metal oxide. .. The method for detecting a fluorine-containing compound gas according to claim 3 , wherein the alkali metal fluoride is at least one selected from the group consisting of NaF and KF. The method for detecting a fluorine-containing compound gas according to claim 3 , wherein the alkali metal hydroxide is at least one selected from the group consisting of NaOH and KOH. The method for detecting a fluorine-containing compound gas according to any one of claims 1 to 5 , wherein the temperature range is 200 to 500 ° C. The method for detecting a fluorine-containing compound gas according to any one of claims 1 to 6, wherein the fluorine-containing compound gas is circulated in a cylinder filled with a filler containing a solid metal oxide. The fluorine-containing compound gas is C ₅ F ₈ And
The solid metal oxide is a silicon oxide,
The method for detecting a fluorine-containing compound gas according to any one of claims 1 to 7, wherein the concentration of the fluorine-containing compound gas is in a concentration range of 0.01 volume ppm or more and 20 volume ppm or less.

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