JPH10286439A - Decomposing method of fluorine-containing compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous decomposition of a perfluoro compd. by bringing a gaseous fluorine-contg. compd. into contact with molecular oxygen and water in the presence of catalyst prepared by depositing at least one kind of metal selected from among 4A, 5A, 6A, 7A, 8 and 1B groups and 3B groups on a carrier. SOLUTION: When a gaseous fluorine-contg. compd. (such as perfluoro compds. and fluorinated hydrocarbons) is decomposed, the fluorine-contg. compd. is brought into contact with molecular oxygen and water in the presence of a catalyst which is prepared by depositing at least one kind of metal selected from among 4A, 5A, 6A, 7A, 8, 1B and 3B groups on a carrier. As for the carrier, for example, alumina such as γ-alumina is preferably used. Its shape is not limited but properly selected according to the reactor and the reaction method. The amt. of the metal deposited is preferably 0.01 to 20 wt.% calculated as a metal to the carrier. As for the molecular oxygen, air is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fluorine-containing compound,
In particular, gaseous fluorinated compounds (perfluoro compounds, fluorinated hydrocarbons, etc.) used for plasma CVD chamber cleaning gas and the like in semiconductor factories, and gaseous fluorinated compounds used for refrigerants and the like ( Freon etc.)
The decomposition method.

[0002]

2. Description of the Related Art Since fluorine-containing compounds (gas-containing fluorine-containing compounds) affect the global environment, for example, by being involved in the destruction of the ozone layer, their emission must be suppressed as much as possible. Of these, perfluoro compounds (hereinafter abbreviated as PFC)
Is a perfluorocarbon in which all the hydrogen atoms of hydrocarbons are replaced with fluorine atoms. Unlike fluorocarbons, they do not contain chlorine and are very stable, so they do not contribute to the destruction of the ozone layer, but they do not contribute to global warming. The coefficient is large and emissions after use may be regulated in the future.

[0003] In order to suppress the emission of such gaseous fluorine-containing compounds, it is necessary to recover or decompose the used exhaust gas by some method. However, considering the simplicity of the method, the latter exhaust gas is required. Is preferred. However, among the fluorine-containing compounds, PFC is very stable, so that it is difficult to treat PFC by a method usually used for decomposition of chlorofluorocarbons. For example, in the method of decomposing by burning together with fuel, a high temperature of 1000 ° C. or more is required. In addition, a method of decomposing using silica, zeolite, or the like as a decomposing agent (Japanese Patent Application Laid-Open No. 7-116466,
No. 132211) requires a high temperature of about 1000 to 1500 ° C. in order to decompose PFC at a sufficient rate. It is complicated and complicated, and further improvement is required.

[0004]

SUMMARY OF THE INVENTION In view of the above technical background, the present invention relates to a method capable of continuously decomposing a fluorine-containing compound (a gaseous fluorine-containing compound), especially PFC, and particularly to a method of continuously decomposing catalytically. It is an object to provide a method that can be used.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for converting a gaseous fluorine-containing compound into a 4A group, a 5A group, a 6A group, and a 7A group.
At least one metal selected from the group consisting of group 8, group 1B and group 3B is brought into contact with molecular oxygen and water in the presence of a catalyst supported on a carrier, Achieved.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the fluorine-containing compound include gaseous fluorine-containing compounds (perfluoro compounds (PFC), fluorinated hydrocarbons, etc.) used as plasma CVD chamber cleaning gases in semiconductor factories. Gaseous fluorine-containing compounds used in refrigerants and refrigerants (such as CFCs)
Is used. These fluorinated compounds (gaseous fluorinated compounds) may be diluted with an inert gas such as helium, argon or nitrogen, or may be used alone or as a mixture of two or more. .

As PFC, CF_Four, C_TwoF₆, C_Three
F₈All hydrogen atoms of hydrocarbons such as
Perfluorocarbons (including saturated and unsaturated),
NF _ThreeSuch as nitrogen fluoride and SF₆Such as sulfur fluoride
No. As the fluorinated hydrocarbon, CH_ThreeF, CH
_TwoF_Two, (CH_TwoF)_TwoPart of hydrogen atoms of hydrocarbons such as
Is substituted with a fluorine atom. Flow
As C_TwoCl_ThreeF_Three(CFC-113), C_Two
Cl_TwoF_Four(CFC-114), C_TwoClF_Five(CFC
-115).

In the present invention, the 4A group, 5A group, 6A group, 7
By bringing the fluorine-containing compound into contact with molecular oxygen and water in the presence of a catalyst in which at least one metal selected from the group A, the group 8, the group 1B, and the group 3B is supported on a carrier, Is decomposed. These metals are compounds, namely halides (such as chlorides),
Inorganic acid salts (nitrates, sulfates, etc.), organic acid salts (oxalates, acetates, etc.), oxyacid salts, oxyacids, organometallic compounds,
It may be supported in the form of an oxide or the like, or may be supported in the form of a metal.

As the Group 4A metal, titanium, zirconium and hafnium can be mentioned. Group 5A metals include vanadium, niobium, and tantalum. 6A
Group metals include chromium, molybdenum, and tungsten. Group 7A metals include manganese, technetium, and rhenium. Group 8 metals include iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium, and platinum. Group 1B metals include copper, silver, and gold. Group 3B metals include boron, gallium, indium, and thallium.

As the carrier, for example, γ-alumina, δ
-Alumina such as alumina and [theta] -alumina are preferably used. The specific surface area of alumina is 120 to ²⁰⁰ m ^2.
/ G is preferred. The shape of the alumina is not particularly limited, and a shape suitable for each, such as a granular shape, a powder shape, and a honeycomb shape, can be selected according to the reactor and the reaction method.

As the method for preparing the catalyst, halides (chlorides, etc.), inorganic acid salts (nitrates, sulfates, etc.), organic acid salts (oxalates, acetates, etc.), oxygen acids, Impregnation method, coprecipitation method, ion exchange method, mechanical kneading using an aqueous solution of an oxyacid salt or a complex (ammine complex or the like) or a solution of an organic metal compound of the metal (aqueous solution or an organic solvent solution such as alcohol). A method in which the metal is supported on a carrier by an ordinary method such as a method. The amount of the metal supported is 0.01 to 50 as a metal on the carrier.
% By weight, particularly preferably 0.01 to 20% by weight. After drying the obtained catalyst, it is preferable to perform normal pretreatment, that is, calcination in air or a stream of an inert gas such as nitrogen. This treatment may be performed using a muffle furnace or the like, or may be performed for several hours before starting the decomposition reaction in the reactor (reaction tube). The firing temperature is preferably from 100 to 800C, particularly preferably from 400 to 700C. If the temperature is too high, the surface area of alumina decreases, which is not preferable.

As the molecular oxygen, oxygen gas diluted with an inert gas such as nitrogen can be used, but air is preferably used. The supply amount of molecular oxygen is not particularly limited as long as it is an amount sufficient to convert the carbon content (carbon atoms) in the fluorine-containing compound into carbon dioxide and carbon monoxide. That is, the supply amount of molecular oxygen is at least equimolar, and preferably about equimolar to about 10-fold molar with respect to the carbon atom in the fluorine-containing compound. The method of supplying molecular oxygen is not particularly limited, and examples thereof include a method of mixing with a fluorine-containing compound and supplying the mixture to a reactor (reaction tube).

In the present invention, water is added to remove halogens (fluorine and chlorine) generated in the decomposition reaction.
Further, when water is added, the catalytic activity is maintained. The amount of water to be added may be at least equimolar to the halogen content (fluorine atom and chlorine atom) in the fluorine-containing compound, and preferably about equimolar to about 10-fold molar. For example, CF
If ₄ 4 moles or more, preferably a 4 to 40-fold moles, C ₂ F ₆ in the case when 6 moles or more, preferably 6
It may be about 60-fold molar. The method of adding water is not particularly limited, and examples thereof include a method of supplying a liquid to a reactor (reaction tube) using a microfeeder, and a method of using a saturator to accompany the fluorine-containing compound.

The decomposition of the fluorine-containing compound of the present invention is carried out, for example, by supplying a mixed gas of the fluorine-containing compound, molecular oxygen and water to a reactor (reaction tube) filled with the catalyst. At this time, the reaction temperature is 300 to 1
000 ° C., preferably 400 to 800 ° C., and the mixed gas supply rate is 50,000 hr ⁻¹ or less, preferably 100 to
It is about 10,000 hr ^-1 . The reaction pressure is 1 to
A wide range from a reduced pressure of rr to a pressurization of 100 atm is possible, but it is preferably from normal pressure to about 10 atm.
The decomposition reaction can be performed by a flow system or a batch system,
The former distribution type is preferred because it is simple. In the case of a flow type, the reaction can be carried out in any of a fixed bed and a fluidized bed.

[0015]

Next, the present invention will be described specifically with reference to examples and comparative examples. The following operations were performed under normal pressure unless otherwise specified. Fluorine-containing compounds (C ₂ F ₆ )
Was determined by the following equation.

[0016]

(Equation 1)

Example 1 A palladium ammine complex [Pd (NH_Three)_FourCl_Two]
(0.01 g) was dissolved in distilled water (30 g).
After adding commercially available granular γ-alumina (10 g) to
To dryness under reduced pressure at 60 ° C using a tally evaporator.
Was. The obtained catalyst (5.0 ml) was dried at 100 ° C.
After that, the reactor was filled into a quartz reaction tube having an inner diameter of 10 mm,
It was baked at 700 ° C. for 1 hour. Then C_TwoF₆/Sky
Gas mixture gas (C _TwoF₆: 1% by volume) at 20 ml / min
Then, supply water to the reaction tubes at 0.36 g / hr, respectively.
The decomposition reaction was performed at the same temperature. C in outlet gas_TwoF₆concentration
(C_TwoF₆Remaining amount) by gas chromatography
When analyzed, C_TwoF₆The conversion was 4 hours after the start of the reaction.
9%. The reaction product is carbon dioxide
Was confirmed by gas chromatography and FT-IR.
Was.

Example 2 A catalyst was prepared in the same manner as in Example 1 except that chloroplatinic acid [H ₂ PtCl ₄ ] (0.1 g) was used instead of the palladium ammine complex. went. As a result, the C ₂ F ₆ conversion was 80% two hours after the start of the reaction.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that γ-alumina (5.0 ml) not supporting a metal was used as a catalyst. As a result, the C ₂ F ₆ conversion was 21% 2 hours after the start of the reaction.

Examples 3 to 11 In Example 1, instead of the palladium ammine complex,
Other than using 0.1 g each of copper nitrate, iron nitrate, cobalt oxalate, chromium nitrate, nickel nitrate, ruthenium chloride, zirconium chloride, indium sulfate, and metavanadic acid,
A catalyst was prepared and reacted in the same manner as in Example 1. Table 1 shows the results.

Examples 12 and 13 In Example 1, instead of the palladium ammine complex,
A reaction was carried out by preparing a catalyst in the same manner as in Example 1 except that 0.5 g of each of metatungstic acid and molybdic acid was used. Table 1 shows the results.

Example 14 In Example 1, after carrying chromium nitrate (0.1 g) in the same manner, a palladium ammine complex [Pd (NH ₃ ) ₄
The reaction was carried out in the same manner as in Example 1 except for using a catalyst similarly supporting [Cl ₂ ] (0.01 g). Table 1 shows the results.

[0023]

[Table 1]

[0024]

According to the present invention, it is possible to use a readily available and relatively inexpensive alumina as a catalyst in a simple reactor and to perform plasma CVD in a semiconductor plant such as PFC which is very stable and difficult to process. It is possible to continuously decompose a fluorine-containing compound used for a chamber cleaning gas or the like. This method is a method for treating a gaseous fluorine-containing compound, which is also very friendly to the global environment because the generated gas is carbon dioxide or the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/26 B01J 23/26 A 23/28 23/28 A 23/30 23/30 A 23/42 23/42 A 23 / 44 23/44 A 23/46 301 23/46 301A 23/72 23/72 A 23/74 23/74 A (72) Inventor Tokuo Matsuzaki 5, 1978 Kogushi, Oji, Ube City, Yamaguchi Prefecture Inside

Claims (3)

[Claims] 1. A gaseous fluorine-containing compound comprising a 4A group,
At least one metal selected from Group A, Group 6A, Group 7A, Group 8, Group 1B, and Group 3B is brought into contact with molecular oxygen and water in the presence of a catalyst supported on a carrier. A method for decomposing a fluorine-containing compound. 2. The method for decomposing a fluorine-containing compound according to claim 1, wherein the fluorine-containing compound is a perfluoro compound, a fluorinated hydrocarbon or chlorofluorocarbon. 3. The method for decomposing a fluorine-containing compound according to claim 1, wherein the carrier is alumina.