JP2004255380A - Treating method for gas containing fluorine compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treating method for decomposition and a catalyst wherein a gas containing a fluorine compound such as C<SB>2</SB>F<SB>6</SB>is effectively decomposed. <P>SOLUTION: F in a gas flow is converted to HF by contacting the gas flow with the catalyst having at least one kind of alumina, titania, silica and zirconia at ca. 400-800 °C in the presence of an effective amount of steam. The gas flow is composed of at least one of a compound having C of two or more and F such as C<SB>2</SB>F<SB>6</SB>, or a compound having N and F. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

The present invention relates to a decomposition treatment method and a catalyst material for efficiently decomposing a fluorine compound-containing gas such as C ₂ F ₆ at a low temperature.

Fluorine compound gases such as C ₂ F ₆ are used in large quantities for semiconductor etching materials, semiconductor cleaning, and the like. However, these substances have been found to be warming substances that, when released into the atmosphere, cause global warming. It is expected that strict regulations will be imposed on the treatment of these compounds after use.

Incidentally, gases such as C ₂ F ₆ contain a large amount of fluorine (F) as a molecular component. Fluorine has the highest electronegativity of all elements and forms a very chemically stable substance. In particular, C ₂ F _{6 and the} like are substances having strong intramolecular forces and poor reactivity. Due to this property, a high temperature is required for decomposition, and a large amount of energy is consumed. Further, in the decomposition reaction at a high temperature, the rate of corrosion of the apparatus material by the generated gas such as hydrogen fluoride is high, and at present, there is no appropriate decomposition treatment method.

  As a decomposition treatment method, a combustion technique at a high temperature is currently being proposed. However, in this method, a large amount of fuel is used, so that the energy efficiency is low, and there is also a problem of damage to the furnace wall due to a halogen compound of 1000 ° C. or more generated during combustion. Therefore, a technology that can decompose at lower temperatures is needed.

As for the catalyst, a TiO ₂ -WO ₃ catalyst has been reported as a catalyst for decomposing an organic halogen compound in Japanese Patent Publication No. 6-59388. This catalyst has a TiO ₂ content of 0.1 to 20.
(If the atomic ratio, Ti is 99.96% or more 92% or less, W 8% or less 0.04% or more) catalyst containing wt% of W is, 375 ° C. to process CCl ₄ order of ppm , A decomposition rate of 99% was maintained for 1500 hours. In organic halogen compounds, the effect as a catalyst poison is larger not only for Cl but also for F. The publication states that organic halogen compounds having 1 carbon atom, that is, CF ₄ , Cl ₂ F _2, etc., can be decomposed, but there is no example of the decomposition result relating to fluorine compounds. In general, an organic halogen compound having 2 carbon atoms is harder to decompose than an organic halogen compound having 1 carbon atom. As another example, an Al ₂ O ₃ —ZrO ₂ —WO ₃ catalyst is reported in JP-A-7-80303 as a decomposition catalyst for a fluorine compound gas. This catalyst burns and decomposes CFCs, and performs a combustion decomposition reaction at 600 ° C. to treat CFC-115 (C ₂ ClF ₅ ), and maintains a decomposition rate of 98% for 10 hours. In this method, since a hydrocarbon such as n-butane is added as a combustion aid, the processing cost increases. Decomposition of a compound consisting only of carbon and fluorine, such as C ₂ F ₆ , is more difficult than that of CFC-115, but there is no example of a decomposition result relating to these substances.

  An object of the present invention is to provide a method and a catalyst for efficiently decomposing a gas containing two or more carbon atoms and containing at least one of a compound containing a fluorine atom or a compound containing a nitrogen atom and a fluorine atom at a low temperature. is there.

  The present inventors have conducted detailed studies on a decomposition treatment method capable of decomposing a fluorine compound-containing gas at a low temperature and with high efficiency, and in which corrosion of an apparatus by hydrogen fluoride released as a decomposition product is less likely to occur. As a result, the present invention has been achieved.

  That is, a gas stream containing two or more carbon atoms and containing at least one of a compound containing a fluorine atom or a compound containing a nitrogen atom and a fluorine atom is passed through a specific fluorine compound decomposition catalyst and a temperature of about 400 to about 800 ° C. It has been found that by contacting in the presence of an effective amount of water vapor, fluorine in the gas stream can be converted to HF. As the decomposition catalyst, a catalyst containing at least one of alumina, titania, silica, and zirconia can be used.

Examples of the fluorine compound include a compound of C and F having 2 or more carbon atoms such as C ₂ F ₆ and a compound of N and F such as NF ₃ .

  Furthermore, it has been found that when at least one of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, and Ni is added to the catalyst, the fluorine compound-containing gas can be decomposed with higher activity. These catalysts are a mixture of alumina, titania, silica, zirconia, and an oxide of at least one of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, Ni, P, and B, or a composite oxide. It is contained in the form of Particularly, in the case of a catalyst containing alumina and titania, the effect is large when the alumina content is 75 wt% or more and 98 wt% or less and the titania content is 25% or less and 2 wt% or more. The effect is great when the oxides of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, Ni, P, and B are contained at 0.1 to 10 wt% with respect to the main catalyst amount.

As a result of various studies for the development of a catalyst for decomposing a fluorine compound-containing gas, it was found that it is necessary to include a metal component that forms a bond with fluorine with an appropriate strength as a property of the catalyst. In particular, in the case of a compound consisting of carbon and fluorine, it has been found that a catalyst containing a metal component having a large enthalpy of formation of fluoride exhibits high decomposition activity because the molecule itself is stable. If a very stable bond is formed, the fluorine compound does not separate from the catalyst, so that the activity gradually decreases. On the other hand, if the bonding strength is too weak, a sufficient decomposition rate cannot be obtained. C ₂ F _6, which is a target gas of the present invention, is a substance having a strong intramolecular force and poor reactivity. When burning these gases, it is said that a temperature of 1500 to 2000 ° C. is required. We have found that the target gas can be decomposed by using alumina, titania, silica, and zirconia alone as a catalyst, but a catalyst containing alumina and titania is a catalyst that can achieve a higher decomposition rate. I found something favorable. Alumina appears to work to attract fluorine compounds onto the catalyst, and titania appears to work to release fluorine compounds on the catalyst.

  It is considered that oxides of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, and Ni exhibit a concerted effect with alumina, titania, silica, and zirconia. Further, it is considered that this contributes to stabilization of titania in the catalyst.

In the method for decomposing a fluorine compound-containing gas of the present invention, it has been found that a fluorine compound such as C ₂ F ₆ may be diluted with an inert gas. By diluting the concentration of the fluorine compound, the load on the catalyst is reduced, and the decomposition activity can be maintained for a long time. As a diluting gas, an inert gas such as Ar, N ₂ , and He can be used.

The fluorine-containing compounds targeted by the present invention are PFCs such as C ₂ F ₆ and NF _3.
(perfluorocompound) or FFC (fully fluorocompound), and the following are typical reactions.

C ₂ F ₆ + 3H ₂ O → CO + CO ₂ + 6HF
C ₂ F ₆ + 2H ₂ O + 1 / 2O ₂ → 2CO ₂ + 6HF
NF ₃ + 3H ₂ O → NO ₂ + 1 / 2O ₂ + 6HF
These fluorine compounds are desirably added to the gas to be treated so that hydrogen atoms are at least equivalent to the F number in the fluorine compound. As a result, F in the compound becomes HF, and F in the decomposition product becomes a form of hydrogen halide which can be easily post-treated. As the hydrogen source at this time, in addition to steam, hydrogen, hydrocarbons, and the like can be used. When hydrocarbons are used, the hydrocarbons burn on the catalyst, and the supplied heat energy can be reduced. it can.

Further, by including an oxidizing gas such as oxygen in the reaction gas, a CO oxidation reaction can be caused at the same time. When the oxidation reaction of CO is incomplete, after removing HF in the decomposition product gas, the CO can be brought into contact with a CO oxidation catalyst to convert CO into CO ₂ .

If the catalyst of the present invention is used, CFCs such as C ₂ Cl ₃ F ₃ , C ₂ Cl ₂ F ₄ and C ₂ ClF ₅ ;
CFC substitutes such as HFC134a, also, can be decomposed even compounds such as SF _6. Also,
Substances such as CCl ₃ F and CCl ₂ F ₂ can also be sufficiently decomposed. Note that Cl in the compound when the chlorine compound is treated is converted to HCl.

  The reaction temperature used in the present invention is preferably from about 400 to about 800C. When used at higher temperatures, a high decomposition rate can be obtained, but the catalyst deteriorates quickly. Also, the corrosion rate of the device material increases rapidly. Conversely, at temperatures below this, the decomposition rate is low.

  As a step of neutralizing and removing the generated HF, a step of washing by spraying an alkali solution is preferred because it is highly efficient and blockage of the piping due to crystal precipitation or the like hardly occurs. A method of bubbling a decomposition product gas in an alkali solution or a method of washing using a packed tower may be used.

  As the Al raw material for preparing the catalyst of the present invention, γ-alumina, a mixture of γ-alumina and δ-alumina, and the like can be used. In particular, it is also a preferable method to use boehmite or the like as an Al raw material and form an oxide by final firing.

  As a Ti raw material for preparing the catalyst of the present invention, titanium sulfate, titania sol, titanium slurry, and the like can be used.

  Further, as a raw material of the third metal component such as Si, Mg, and Zr, various kinds of nitrates, ammonium salts, chlorides, and the like can be used.

  As a method for producing the catalyst of the present invention, any of a precipitation method, an impregnation method, a kneading method and the like usually used for production of a catalyst can be used.

  Further, the catalyst in the present invention can be used as it is formed into granules, honeycombs or the like. As the molding method, an arbitrary method such as an extrusion molding method, a tablet molding method, a tumbling granulation method, or the like can be adopted according to the purpose. Further, it can be used by coating on a honeycomb or a plate made of ceramics or metal.

  The fluorine compound-containing gas treatment method of the present invention can decompose a fluorine compound at a lower temperature than other treatment methods.

  When treating a gas containing a fluorine compound, corrosion of equipment materials due to acid components such as HF generated by decomposition becomes a problem. However, according to the present invention, since the temperature used is relatively low, the corrosion rate is low. Slowly, maintenance of the device becomes unnecessary.

  The apparatus for carrying out the method for treating a fluorine compound-containing gas of the present invention only needs to be provided with a catalyst reaction tank for decomposing a fluorine compound and a facility for neutralizing and removing an acid component in a decomposition product gas, and the apparatus can be downsized.

According to the present invention, a fluorine-containing gas such as C ₂ F ₆ and NF ₃ can be efficiently decomposed.

  Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to only these examples.

  FIG. 1 shows an embodiment in which the decomposition treatment method of the present invention is used in a cleaning step of a plasma CVD apparatus in a semiconductor production process.

A plasma CVD apparatus is an apparatus for forming a SiO ₂ film on a semiconductor wafer surface by a vapor deposition method. However, since the SiO ₂ film adheres to the entire inside of the apparatus, it is necessary to remove SiO ₂ attached to unnecessary portions. C ₂ F ₆ is used to clean this SiO ₂ . The cleaning gas containing C ₂ F ₆ is sent to a CVD chamber and excited by plasma to remove SiO ₂ . Thereafter, the inside of the chamber is replaced with N ₂ , the C ₂ F ₆ concentration is diluted to about 3 to 5%, and the chamber is discharged at about 15 l / min.

Air 3 was added to the exhaust gas to dilute C ₂ F ₆ . The reaction gas 5 obtained by further adding steam 4 to the dilution gas is sent to a decomposition step. The concentration of C ₂ F ₆ in the reaction gas is about 0.5%. In the decomposition step, the reaction gas 5 is mixed with the Al ₂ O ₃ catalyst at 700 ° C. under the condition of a space velocity of 3000 per hour (space velocity (h （ ¹ ) = reaction gas flow rate (ml / h) / catalyst amount (ml)). Make contact. In this case, the reaction gas may be heated, or the catalyst may be heated by an electric furnace or the like. The decomposition gas 6 is sent to an exhaust gas cleaning step. In the exhaust gas cleaning step, an alkaline aqueous solution is sprayed on the decomposition gas 6, and the exhaust gas 7 from which the acid component in the decomposition gas has been removed is discharged out of the system. The decomposition rate of C ₂ F ₆ is determined by analyzing the reaction gas 5 and the exhaust gas 7 using FID (abbreviation of Flame Ionization Detector) gas chromatograph and TCD (abbreviation of Thermal Conductivity Detector) gas chromatograph, and calculating the material balance at the entrance and exit. Ask.

  Hereinafter, the results of examining the activities of various fluorine compound decomposition catalysts will be described.

[Example 1]
And diluted by adding air to the C ₂ F ₆ gas having 99% or more. Steam was further added to this dilution gas. Water vapor was supplied to the upper portion of the reaction tube at 0.11 ml / min by using a micro tube pump to gasify the water. The C ₂ F ₆ concentration in the reaction gas was about 0.5%. The reaction gas was brought into contact with the catalyst heated to 700 ° C. from the outside of the reaction tube by an electric furnace at a space velocity of 3000 per hour.

The reaction tube is an Inconel reaction tube having an inner diameter of 19 mm, has a catalyst layer at the center of the reaction tube, and has an Inconel thermocouple protection tube having an outer diameter of 3 mm inside. The decomposition product gas that passed through the catalyst layer was bubbled into a sodium hydroxide solution and released outside the system. The decomposition rate of C ₂ F ₆ is
It was determined by the following equation using a FID gas chromatograph and a TCD gas chromatograph.

  The preparation method of each catalyst used in the test under the above conditions is shown below.

Catalyst 1; Al ₂ O ₃
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical Co., Ltd. was pulverized, sieved to a particle size of 0.5-1 mm, dried at 120 ° C. for 2 hours, and calcined at 700 ° C. for 2 hours and subjected to a test.

Catalyst 2; TiO ₂
Granular titania (CS-200-24) manufactured by Sakai Chemical Co., Ltd. was pulverized, sieved to a particle size of 0.5-1 mm, dried at 120 ° C. for 2 hours, and calcined at 700 ° C. for 2 hours and subjected to a test.

Catalyst 3; ZrO ₂
200 g of zirconyl nitrate was dried at 120 ° C. for 2 hours and calcined at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved, granulated into zirconia having a particle size of 0.5-1 mm, and subjected to a test.

Catalyst 4; SiO ₂
Granulated silica (CARIACT-10) manufactured by Fuji Silysia was crushed, sieved to a particle size of 0.5-1 mm, dried at 120 ° C. for 2 hours, and calcined at 700 ° C. for 2 hours and subjected to a test.

Catalyst 5; TiO ₂ -ZrO ₂
Granular titania (CS-200-24) manufactured by Sakai Chemical was pulverized to 0.5 mm or less. 78.3 g of zirconyl nitrate was added to 100 g of this powder, and kneaded while adding pure water. After kneading, the mixture was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. Put the obtained powder in a mold,
Compression molding was performed at a pressure of 500 kgf / cm ² . The molded product was pulverized, sieved, granulated to a particle size of 0.5-1 mm, and subjected to a test.

Catalyst 6; Al ₂ O ₃ -MgO
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical was pulverized to a particle size of 0.5 mm or less. 56.4 g of magnesium nitrate was added to 100 g of this powder, and kneaded while adding pure water. After kneading, the mixture was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved to give a test particle size of 0.5-1 mm.

Catalyst 7; Al ₂ O ₃ —TiO ₂
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical was pulverized to a particle size of 0.5 mm or less. 56.4 g of a dry powder of metatitanate slurry was added to 100 g of this powder, and kneaded while adding pure water. After kneading, the mixture was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 8; Al ₂ O ₃ —SiO ₂
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical was pulverized to a particle size of 0.5 mm or less. 13.2 g of a dry powder of SiO ₂ sol was added to 100 g of this powder, and kneaded while adding pure water. After kneading, the mixture was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

  FIG. 2 shows the test results of the catalysts 1 to 8.

[Example 2]
In this example, the effect of the addition of the third component was examined under the same conditions as in Example 1. Each catalyst was prepared as follows.

Catalyst 9; Al ₂ O ₃ —TiO ₂
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical Co., Ltd. was pulverized, sieved to a particle size of 0.5-1 mm, and dried at 120 ° C. for 2 hours. This was impregnated with 176 g of a 30% titanium sulfate solution. After impregnation, it was dried at 250 to 300 ° C. for about 5 hours and baked at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 10; Al ₂ O ₃ —TiO ₂ —ZrO ₂
Granular alumina (NKHD-24) manufactured by Sumitomo Chemical Co., Ltd. was pulverized, sieved to a particle size of 0.5-1 mm, and dried at 120 ° C. for 2 hours. This was impregnated with 176 g of a 30% titanium sulfate solution. After the impregnation, the catalyst was dried at 250 to 300 ° C. for about 5 hours and calcined at 700 ° C. for 2 hours to prepare Catalyst A. Subsequently, 50 g of the catalyst A was impregnated with an aqueous solution in which 6.7 g of zirconyl nitrate dihydrate was dissolved in 90 g of H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 11; Al ₂ O ₃ —TiO ₂ —WO ₃
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution obtained by dissolving 6.5 g of ammonium paratungstate in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 12; Al ₂ O ₃ —TiO ₂ —SiO ₂
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution in which 7.5 g of 20 wt% silica sol was dissolved in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 13; Al ₂ O ₃ —TiO ₂ —SnO ₂
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of Catalyst A was impregnated with 90 g of an aqueous solution in which 5.6 g of tin chloride dihydrate was dissolved in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 14; Al ₂ O ₃ —TiO ₂ —CeO ₂
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution obtained by dissolving 10.9 g of cerium nitrate hexahydrate in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 15; Al ₂ O ₃ —TiO ₂ —MnO ₂
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of Catalyst A was impregnated with 90 g of an aqueous solution in which 7.2 g of manganese nitrate hexahydrate was dissolved in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 16; Al ₂ O ₃ —TiO ₂ —Bi ₂ O ₃
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution in which 7.4 g of bismuth nitrate hexahydrate was dissolved in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 17; Al ₂ O ₃ —TiO ₂ —NiO
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution in which 7.3 g of nickel nitrate hexahydrate was dissolved in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

Catalyst 18; Al ₂ O ₃ —TiO ₂ —BO ₄
Catalyst A was prepared in the same manner as for catalyst 10. Subsequently, 50 g of the catalyst A was impregnated with 90 g of an aqueous solution obtained by dissolving 12.0 g of ammonium borate octahydrate in H ₂ O. After impregnation, it was dried at 120 ° C. for 2 hours and fired at 700 ° C. for 2 hours. This was subjected to a test.

  FIG. 3 shows the activities of the catalysts 9 to 18 and the catalyst 1 in Example 1.

[Example 3]
In this example, various catalysts were prepared by changing the alumina raw material and the titania raw material, and the activity was examined in the same manner as in Example 1.

Catalyst 19; Al ₂ O ₃
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 2 hours. 200 g of the dried powder was fired at 300 ° C. for 0.5 hour, and the firing temperature was raised to 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 20; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. 200 g of this dry powder and 248.4 g of a 30% titanium sulfate solution were kneaded while adding about 200 g of pure water. After kneading, the mixture was dried at 250 to 300 ° C. for about 5 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 21; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. 200 g of this dry powder and about 100 g of an aqueous solution obtained by adding pure water to 78.6 g of 30% titania sol were kneaded. After kneading, the mixture was dried at 120 ° C. for about 2 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

  FIG. 4 shows the results obtained by examining the activities of the catalysts 19 to 21 in the same manner as in Example 1.

[Example 4]
This example is a result of preparing a catalyst in which the composition of Al and Ti in the catalyst 20 of Example 3 was changed and examining the activity.

Catalyst 22; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. 100 g of this dry powder and 48.8 g of a 30% titanium sulfate solution were kneaded while adding about 150 g of pure water. After kneading, the mixture was dried at 250 to 300 ° C. for about 5 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 23; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. 100 g of this dry powder and 82.4 g of a 30% titanium sulfate solution were kneaded while adding about 120 g of pure water. After kneading, the mixture was dried at 250 to 300 ° C. for about 5 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 24; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. 100 g of this dry powder and 174.4 g of a 30% titanium sulfate solution were kneaded while adding about 70 g of pure water. After kneading, the mixture was dried at 250 to 300 ° C. for about 5 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved and subjected to a test with a particle size of 0.5-1 mm.

Catalyst 25; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. The mixture was kneaded while adding 100 g of this dry powder and 392 g of a 30% titanium sulfate solution. After kneading, the mixture was dried at 250 to 300 ° C. for about 5 hours and fired at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved to give a test particle size of 0.5-1 mm.

FIG. 5 shows the results obtained by examining the activities of the catalysts 22 to 25 in the same manner as in Example 1.
[Example 5]
This embodiment is an example in which sulfuric acid is added during catalyst preparation.

Catalyst 26; Al ₂ O ₃ —TiO ₂
The boehmite powder (PURAL SB) manufactured by CONDEA was dried at 120 ° C. for 1 hour. To 150 g of the dried powder, an aqueous solution obtained by diluting 58.8 g of a 30% titania sol solution of CS-N manufactured by Ishihara Sangyo and 44.8 g of a 97% sulfuric acid solution with 250 ml of pure water was added and kneaded. After kneading,
It was dried at 250-300 ° C. for about 5 hours and baked at 700 ° C. for 2 hours. The obtained powder was put into a mold and compression-molded under a pressure of 500 kgf / cm ² . The molded product was pulverized and sieved to give a test particle size of 0.5-1 mm. The test conditions were the same as in Example 1 except that the space velocity was set to 1000 per hour. As a result of the test, a decomposition rate of C ₂ F ₆ of 80% was obtained at a reaction temperature of 650 ° C.

FIG. 4 is a process chart showing a processing process according to an embodiment of the present invention. It is a graph which shows the performance of various fluorine compound decomposition catalysts. It is a graph which shows the performance of various fluorine compound decomposition catalysts. It is a graph which shows the performance of various fluorine compound decomposition catalysts. It is a graph which shows the performance of various fluorine compound decomposition catalysts.

Explanation of reference numerals

_{1 ... C 2 F 6, 2} ... N 2, 3 ... air, 4 ... steam, 5 ... reaction gas, 6 ... cracked gas, 7 ... exhaust gas.

Claims (6)

  A gas stream containing at least one of a compound containing two or more carbon atoms and containing a fluorine atom or a compound containing a nitrogen atom and a fluorine atom is mixed with a catalyst containing at least one of alumina, titania, silica, and zirconia by about 400 to 800. A method for treating a fluorine compound-containing gas, comprising the step of contacting at a temperature of ° C in the presence of an effective amount of steam to convert F in said gas stream to HF.   The method according to claim 1, wherein the fluorine compound-containing gas is a compound of C and F or a compound of N and F containing two or more carbon atoms.   2. The method according to claim 1, wherein the catalyst further contains at least one of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, and Ni. .   A catalyst for treating a gas stream containing at least one of a compound of C and F or a compound of N and F containing two or more carbons, comprising alumina and titania, wherein the alumina is 75 wt% or more and 98 wt% or less; A fluorine compound decomposition catalyst, wherein titania is 25 wt% or less and 2 wt% or more.   5. The catalyst according to claim 4, further comprising at least one of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, Ni, P and B.   The catalyst according to claim 5, wherein the oxides of Si, Mg, Zr, W, Sn, Ce, Mn, Bi, Ni, P, and B are contained in an amount of 0.1 wt% to 10 wt% based on the main amount of the alumina-titania catalyst. A fluorine compound decomposition catalyst, characterized by comprising

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