JPH09173773A - Method for removing perfluoroolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and continuously remove perfluoroolefins in a liq. or gas until a sufficiently low concn. is attained by bringing gaseous fluorine into contact with the liq. or gas. SOLUTION: Gaseous fluorine is brought into contact with a liq. or gas contg. perfluoroolefins such as perfluoroisobutylene and perfluorocyclobutene at 0-30 deg.C for a slit time of 0.1-300sec, preferably 1-60sec by a batch system, a continuous system, etc. The perfluoroolefins are decomposed at the double bond parts or fluorine is added to the double bond parts and the perfluoroolefins are removed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for removing perfluoroolefin by bringing a gas or liquid containing perfluoroolefin into contact with fluorine gas. More specifically, it relates to a method for substantially detoxifying a toxic perfluoroolefin.

[0002]

2. Description of the Related Art Perfluoro compounds are widely used as dry etchants in semiconductor manufacturing, cooling media for electronic devices, insulating materials for transformers, heat media for vapor phase soldering, and the like. However, when the perfluoro compound is heated to a high temperature or when the perfluoro compound is produced, a highly toxic perfluoro olefin may be produced as a by-product. For example, perfluoroisobutylene (hereinafter referred to as PFIB) is a by-product due to thermal decomposition of tetrafluoroethylene resin, vapor phase soldering using perfluorotripentylamine, or thermal decomposition of tetrafluoroethylene, chlorodifluoromethane, and trifluoromethane. To do.

Among the perfluoroolefins, PFIB
Is extremely toxic with a 4-hour lethal inhalation toxicity (ALC) of 0.5 ppm, and is colorless and odorless, and it takes time to develop subjective symptoms (Ishikawa et al., Fluorine compound, p.
10, Kodansha, 1979). In addition, PFIB is designated as a Class 1 designated substance in the Act on the Prohibition of Chemical Weapons and the Regulation of Specific Substances. Furthermore, as a permissible concentration of PFIB, a value of 10 ppb or less is adopted in some countries (ILO Occupatuinal Safety and He
alth series No.37, 1977).

Since PFIB is highly toxic, P
Various methods have been proposed to remove FIB. That is, a method of contacting with alcohols (JP-A-53-73504), a method of contacting with ammonia (JP-B-50-16768), and the like. However,
None of these methods can easily remove PFIB to a sufficiently low concentration of 10 ppb or less, or a large-scale device or a complicated device is required to remove PFIB over a long period of time or continuously. Further, a problem is a waste treatment method of chemical substances brought into contact with PFIB.

[0005]

A method for removing perfluoroolefins from a gas or liquid containing perfluoroolefins can easily remove perfluoroolefins to a sufficiently low concentration without requiring a large-scale device or a complicated device. It has been desired to develop a removal method that can be removed continuously.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the above problems. As a result, they have found that the above object can be achieved by bringing a gas or liquid containing perfluoroolefin into contact with fluorine gas, and have completed the present invention.

That is, the present invention is a method for removing perfluoroolefin, characterized in that a gas or liquid containing perfluoroolefin is brought into contact with fluorine gas.

As the perfluoroolefin to be removed in the present invention, those having a carbon-fluorine bond and having at least one double bond in the molecule are applied without any limitation. Among these, compounds having 2 or more carbon atoms, preferably 2 to 6 carbon atoms are preferable. Typical perfluoroolefins to which the present invention is applicable include PFIB,
Examples include perfluorocyclobutene and hexafluoropropene. Of these, PFIB, which is particularly highly toxic, is preferably targeted.

In the present invention, a gas or liquid containing perfluoroolefin at room temperature and atmospheric pressure is targeted. The concentration of the perfluoroolefin in the gas or liquid containing the perfluoroolefin is preferably 1% or less, which cannot be easily reduced by distillation or the like. Further, those in which the perfluoroolefin is diluted with an inert gas such as nitrogen or helium, air, hydrogen fluoride, a gas or a liquid perfluoro compound, etc. are preferably targeted. Examples of gas or liquid perfluoro compounds include perfluoroalkanes such as perfluoromethane, perfluoroethane, perfluoropropane, perfluorobutane, perfluoropentane, perfluorohexane and perfluorononane,
Perfluorocycloalkanes such as perfluorocyclohexane, perfluoromethylcyclohexane, perfluoropolyhydrophenanthrene, perfluoropolycyclic compounds such as perfluorodecalin, nitrogen trifluoride, perfluorotrimethylamine, perfluorotriethylamine, perfluorotripropylamine, perfluorotributylamine, perfluorotritriamine. Pentylamine, perfluoromorpholine, perfluoro-N-methylmorpholine, perfluoro-N-ethylmorpholine,
Perfluoro-N-propylmorpholine, perfluoro-N-butylmorpholine, perfluoro-nitrogen-containing compounds such as perfluoro-N, N-dimethylcyclohexylamine, perfluoro-2-propyltetrahydropyran,
Examples thereof include oxygen-containing compounds such as perfluoro-2-butyltetrahydrofuran and perfluorobutyl ether, and sulfur-containing compounds such as sulfur hexafluoride and perfluorooctylsulfapentafluoride. In the present invention, the gas or liquid containing the perfluoroolefin is particularly a gas or liquid of the composition which may be generated when a specific perfluoro compound is heated to a high temperature or when a specific perfluoro compound is produced. Is preferred.

The fluorine gas used in the present invention is
The fluorine gas generated in the fluorine electrolysis cell, the fluorine gas in a commercially available fluorine cylinder, or the exhaust gas containing the fluorine gas used in the reaction or the like may be used as it is or diluted with an inert gas such as nitrogen or helium. In the present invention, by contacting a gas or liquid containing the perfluoroolefin with the fluorine gas, the perfluoroolefin is decomposed at the double bond portion, or fluorine is added to the double bond portion, The perfluoroolefin is removed. Here, the concentration of the fluorine gas may be a dilute concentration, and is usually in the range of 0.01 to 20%, preferably 0.5 to 5%. If the concentration of fluorine gas is lower than the above range, the perfluoroolefin cannot be sufficiently removed. The concentration of fluorine gas may be higher than the above range, but there is no particular merit because the utilization rate of fluorine gas decreases.

The temperature at which the gas or liquid containing the perfluoroolefin is brought into contact with the fluorine gas is usually normal temperature, and may be 0 to 30 ° C. The contact time may be short and may be 0.1 to 300 seconds, preferably 1 to 60 seconds.
Here, the contact time is the time during which the gas or liquid containing the perfluoroolefin stays in the container for contacting the gas or liquid containing the perfluoroolefin with the fluorine gas. If the contact time is shorter than the above range, the perfluoroolefin cannot be sufficiently removed.
The contact time may be longer than the above range, but it does not bring any merit because it causes an increase in the size of equipment.

The method for bringing the gas or liquid containing perfluoroolefin into contact with fluorine gas is batch type, continuous type, countercurrent type, cocurrent type, bubble column type, spray column type,
A known method such as a stirring tank type or a mixing tank type may be adopted. As the material of the device, general-purpose materials such as iron and stainless steel may be used. According to the present invention, since the perfluoroolefin can be sufficiently removed in a short time, a method of continuously contacting the gas or liquid containing the perfluoroolefin with the fluorine gas is particularly preferable.

According to the present invention, the concentration of the perfluoroolefin is 10 ppb or less, preferably 5 ppb, by bringing the perfluoroolefin and the fluorine gas into contact with each other.
It can be easily and continuously removed up to the following. In addition, perfluoroolefins can be decomposed into harmless perfluoroalkanes.

After the gas or liquid containing the perfluoroolefin is brought into contact with the fluorine gas, the excess fluorine gas may be absorbed in an alkaline aqueous solution or the like.

In the present invention, the most preferred embodiment will be exemplified. PFIB such as heat treatment of a perfluoro compound
Such as by-production of highly toxic perfluoroolefin by which a gas or liquid containing perfluoroolefin flows, a step of releasing an exhaust gas containing fluorine gas using fluorine gas such as a fluorination reaction, and the above-mentioned fluorine gas or Further, in a manufacturing process having a detoxification step of absorbing an exhaust gas containing an acidic gas using an alkaline aqueous solution or the like, an exhaust gas containing a fluorine gas is introduced into a step in which a gas or a liquid containing a perfluoroolefin flows to remove the perfluoroolefin. After that, a mode in which the exhaust gas is then introduced into the harm removal process can be mentioned.

[0016]

According to the present invention, perfluoroolefin can be almost completely removed by a simple operation of bringing a gas or liquid containing perfluoroolefin into contact with fluorine gas. Furthermore, continuous removal over a long period of time can be easily performed.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 Gas composition and concentration were 160 ppm of PFIB, 1500 ppm of perfluorobutane, 6000 ppm of perfluoropentane, and 1100 pp of hexafluoropropene.
m, perfluoro-2-butene of 290 ppm, and the remaining gas mixture was nitrogen gas. This mixed gas was passed through a pipe made of SUS having an inner diameter of 28 mm having a sampling port, and fluorine gas diluted to a predetermined concentration shown in Table 1 was heated at a temperature of 15 ° C.
Were continuously contacted in parallel. The distance from the contact start position with the fluorine gas to the sampling port is 1 m.

The exhaust gas brought into contact with the fluorine gas from the sampling port was sampled in a closed container, passed through a 30 wt% potassium iodide aqueous solution at room temperature to absorb the fluorine gas, and collected in a Tedlar bag. P in the collected gas
The concentration of FIB was analyzed by gas chromatography with a non-radiation source type electron capture detector. The analysis results are shown in Table 1 together with the contact time.

Further, in Table 1, No. The concentrations of perfluoroolefins other than PFIB in the gas after being contacted with fluorine gas under the condition of 3 were 10 ppb or less for both hexafluoropropene and perfluoro-2-butene.

Further, in Table 1, No. When the PFIB concentration in the exhaust gas was measured after continuously operating for 1 month under the condition of No. 3, it was 0.1 ppb or less.

[0022]

[Table 1]

Comparative Example 1 400 ml of each of the various solutions shown in Table 2 was placed in a 500 ml washing bottle having a filter (area: 3 cm ² ) having a pore size of 100 to 120 μm, and the mixed gas used in Example 1 was 6%.
Contact was carried out at a temperature of 15 ° C., flowing through at 0 ml / min. The exhaust gas after contact was collected in a Tedlar bag for 10 minutes from the start of contact, and the PFIB concentration was analyzed.
The analysis results are also shown in Table 2.

[0024]

[Table 2]

Example 2 A SUS reactor having an inner diameter of 28 mm and a length of 50 cm was supplied with a 2% concentration of fluorine gas at a rate of 12 ml / min from the bottom, and 300 ml / perfluorotripentylamine having a PFIB concentration of 80 ppm from the top. Minute (contact time 59 seconds)
Was supplied continuously.

The perfluorotripentylamine after the countercurrent contact was overflowed and collected in a closed container. The recovery rate was 99.99%. The PFIB concentration in the recovered perfluorotripentylamine was 0.1 ppb or less.

PF in perfluorotripentylamine
Regarding the IB concentration, before and after contacting with fluorine gas, the perfluorotripentylamine was put in a 500 ml washing bottle, nitrogen gas was passed through this, and this exhaust gas was filled with a 30 wt% potassium iodide aqueous solution. After passing through an air-washing bottle, it was collected in a Tedlar bag to determine the PFIB concentration.

Claims (2)

[Claims] 1. A method for removing perfluoroolefin, which comprises bringing a gas or liquid containing perfluoroolefin into contact with fluorine gas. 2. The concentration of perfluoroolefin is 10 pp.
The method for removing perfluoroolefin according to claim 1, wherein the method removes up to b or less.