JPH10202061A - Treatment of gas containing organic halogen compound and catalyst for decomposition of organic halogen compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decompose an org. halogen compd. with a catalyst maintaining its performance for a long time and to produce the catalyst for decomposition. SOLUTION: A flow of gas contg. less than 10vol.% org. halogen compd. is brought into contact with a catalyst contg. titania, silica and tungsten oxide as titania surface-coated with a porous layer of silica and tungsten oxide in the presence of less than 30vol.% steam based on the total flow rate of the gas to treat the org. halogen compd. The concn. of the silica is 0.5 to <2wt.% of that of the titania, and the titania and tungsten oxide are contained so that the molar ratio between Ti and W is regulated to (20-95):(80-5). The temp. of the flow does not exceed 500 deg.C. The org. halogen compd. is decomposed into CO, CO2 and hydrogen halide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to halogens of fluorine, chlorine and bromine such as chlorofluorocarbons (CFCs, for example, chlorofluorocarbons) and hydrofluorocarbons (HCFCs, for example, chlorofluorocarbons). The present invention relates to a catalyst exhibiting high activity against the decomposition of organic compounds and maintaining the activity for a long time, and a method for producing the same.

[0002]

2. Description of the Related Art Organic halogen compounds containing fluorine, chlorine, and bromine in organic compounds, such as chlorofluorocarbon, hydrofluorocarbon, trichloroethylene, methyl bromide, and halon, have been widely used as blowing agents, refrigerants, fire extinguishers, and the like. Was. It has been pointed out that these compounds cause destruction of the ozone layer and warming, and have serious effects on the environment, such as generation of carcinogenic substances. Are being considered.

[0003] Since the recovered organic halogen compounds are relatively stable compounds having low reactivity, at present, there is no appropriate decomposition treatment technology. Further, the decomposition products contain corrosive halogen gas, which makes the decomposition processing technology more difficult. The decomposition method mainly includes a combustion technique at a high temperature and a plasma technique. However, this method uses a large amount of fuel and electric power, has low energy efficiency, and has a problem that the generated halogen damages the furnace wall. In particular, in the plasma method, when the content of the organic halogen compound in the processing gas is low, the energy loss is large. On the other hand, a decomposition method using a catalyst is an efficient and excellent method that can be processed with low energy if the performance of the catalyst is sufficiently high.

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 W content of 0.1 to ₂₀ wt% of TiO _2.
(In terms of atomic ratio, Ti is 92% or more and 99.
96% or less, W is 8% or less, 0.04% or more)
Decomposition rate of 9 at 375 ° C for processing mCl CCl ₄
9% was retained for 1500 hours. However, in the organic halogen compound, the effect as a catalyst poison is not only Cl but also F. Therefore, a halogen-resistant catalyst that does not easily react with both halogen elements of Cl and F is required.

[0005]

The present invention suppresses the reaction with F and Cl in an organic halogen compound, and
An object of the present invention is to provide a high-performance catalyst for decomposing an organic halogen compound capable of maintaining its performance, a production method, an apparatus, and a processing method.

[0006]

Means for Solving the Problems The present inventors have developed a high-performance catalyst which can decompose an organic halogen compound with high efficiency and which is hardly deteriorated by halogens, particularly F, contained in reactants and decomposition products. As a result of conducting the search in detail, the present invention was reached. That is, it contains titania, silica, and tungsten oxide, and the silica is contained in an amount of 0.5% by weight or more based on the titania.
% By weight, and titania and tungsten oxide having an atomic ratio of Ti to W in which Ti is 20 mol% or more and 95 mol%.
A catalyst in which W is 80 mol% or less and 5 mol% or more, and at least the surface of titania is covered with at least one porous layer of silica and tungsten oxide;
A method for treating an organic halogen compound by contacting a gas stream containing an organic halogen compound not exceeding vol% with a catalyst, wherein the gas stream is heated at a temperature not exceeding 500 ° C. and not exceeding 30 vol% of a total gas flow rate. To decompose the organic halogen compound into carbon monoxide, carbon dioxide and hydrogen halide. When the catalyst has a porous layer of silica on the surface of titania particles, and further has a porous layer of tungsten oxide on the surface of the porous layer of silica, the catalyst exhibits excellent decomposition activity, particularly high durability. I found it. It has also been found that the same excellent decomposition activity is exhibited when a porous layer of tungsten oxide is provided on the surface of titania particles and a porous layer of silica is further provided on the surface of the porous layer of tungsten oxide. This catalyst contains silica, titanium and tungsten in the form of a mixture of oxides or a composite oxide.

[0007] Titania exhibits high activity against the decomposition of organic halogen compounds. However, if F is present in the reaction gas, it forms a compound called TiOF _{2 and} is easily desorbed from the catalyst, so that the active sites are reduced. It was found that the activity gradually decreased.

Therefore, it is necessary to provide a long life without impairing the high activity of titania. As a result of searching for a metal oxide which has low reactivity with F, that is, a metal oxide which is difficult to form F, it was found that tungsten oxide hardly reacts with F. Therefore, it is desirable that only tungsten oxide exhibit high activity, but only tungsten oxide has a small specific surface area and low activity. As a method of increasing the specific surface area of the tungsten oxide, there is a method of dispersing it on titania, tungsten oxide, zeolite, or the like. In particular, when silica or tungsten oxide is mixed with titania, the amount of active sites (particularly strong acid sites) is increased. increased. It is known that silica alone reacts with F when decomposing an organic halogen compound. However, it was found that when combined with titania, the strong acid sites in the catalyst increased and exceeded the activity of titania alone. These acid sites are hardly deteriorated with respect to the decomposition products HF and HCl, and maintain high activity. Therefore, if a porous layer of tungsten oxide is formed on the surface of the particles in which titania and silica are mixed or formed into a complex oxide, without impairing the activity of titania,
It was thought that catalyst life could be extended.

As a method for forming a porous layer of silica or tungsten oxide on the surface of titania particles, an impregnation method in which a solution containing silica or a solution containing W is impregnated into titania particles and fired is used. When silica or tungsten oxide is in excess, the surface of the titania granulated particles formed by assembling fine titania particles one by one can also be coated with excess silica or W ions.

The titania particles can be prepared by applying a solution containing silica or W to the titania particles or by a vapor deposition method. In these methods, the surface of the titania particles can be coated with a small amount of W.

The thickness of the porous layer of silica and tungsten oxide covering the surface of the titania particles is preferably 1 μm or more and 1 mm or less.

In order to cover the surface of the titania particles with silica or tungsten oxide, an appropriate amount of silica or tungsten oxide is required. In particular, titania particles having a particle size of 2 to 4 mm are impregnated with a porous layer of tungsten oxide by an impregnation method. When it is formed, the titania and tungsten oxide in the catalyst must be converted so that the atomic percentage of W to Ti is not more than 10%.
It was found that the surface of the titania particles could not be completely covered. On the other hand, in order to form a porous layer of silica by impregnation on titania particles having a particle size of 2 to 4 mm, silica is used in an amount of 0.1 to 0.1% with respect to titania.
It was found that the content of titania alone was improved when the content was 5% by weight or more and less than 2% by weight. In the case of the impregnating treatment, the tungsten oxide can be dispersed also in the inside of the titania grains.
mol% or more and 90 mol% or less, W is 80 mol% or less 10 mol
% Or more is desirable. In particular, when the organic halogen compound is a molecule having 1 carbon atom, the atomic ratio between Ti and W is such that Ti is 40
mol% or more and 90 mol% or less, W is 60 mol% or less 10 mol%
It is preferable that it is above. In the case of a molecule having 2 carbon atoms, the number of halogen elements contained in the molecule increases, so that the atomic ratio between Ti and W is set to 20 mol% or more and 85 mol
% And W is preferably 80 mol% or less and 15 mol% or more, and the surface of the titania particles is preferably thickly laminated. Desirably, the silica is in each case in the range of about 0.5% to less than 2% by weight relative to titania. As the solution containing W used in the impregnation treatment, an aqueous solution in which an ammonium salt of W is dissolved in aqueous hydrogen peroxide can be used.

The granular titania in the present invention is most effectively formed by the rolling granulation method. In this case, the amount of pores inside the catalyst can be easily adjusted.

Further, it has been found that a catalyst to which at least one of sulfur, phosphorus, molybdenum and vanadium is added as the fourth component improves the durability of the catalyst. That is, in the catalyst composed of titania, silica and tungsten oxide,
Further, it has been found that the effect is great when S, Mo, and V are present at 0.001 to 10 mol% with respect to titanium atoms as a fourth component.

The catalyst according to the present invention can be used as it is in the form of granules, pellets, 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 and the like can be adopted according to the purpose. In this case, alumina cement, calcium-sodium cement, other ceramics and organic components can be mixed for the purpose of improving strength and increasing specific surface area. Needless to say, the catalyst component can be supported on a particulate carrier such as alumina or silica by impregnation or the like. Further, it can be used after being coated on a honeycomb or plate made of ceramics or metal.

As the titanium raw material for preparing the catalyst of the present invention, titanium oxide, various titanic acids which generate titanium oxide by heating, titanium sulfate, titanium chloride, organic titanium compounds and the like can be used.

These titanium raw materials are converted to water, ammonia water,
It is also a preferable method to form a precipitate of hydroxide with an alkali solution or the like and to form an oxide by final baking.

As the silica raw material, silica sol or the like can be used.

Further, the tungsten raw material is preferably tungsten oxide, tungstic acid, ammonium paratungstate or the like. A raw material containing both phosphorus and tungsten, such as ammonium phosphotungstate, can also be used.

The catalyst of the present invention is less susceptible to deterioration as the active sites in the catalyst are more acidic, and it is also effective that the catalyst contains a component such as S or P which enhances the catalytic acidity. S exists in the form of oxide ions such as sulfate ions.

The organic halogen compounds to be used in the present invention include various chlorofluorocarbons (fluorocarbons), hydrofluorocarbons (alternative fluorocarbons), trichloroethylene,
Compounds containing fluorine, chlorine and bromine in organic compounds such as methyl bromide.

Taking Freon 113, Freon 12 and methyl bromide as examples, the following reactions are typical.

[0023]

Embedded image CCl ₂ F—CCIF ₂ + 3H ₂ O → CO + CO ₂ + 3HCl + 3HF (Formula 1)

[0024]

[Chemical Formula 2] CCl ₂ F ₂ + 2H ₂ O → CO ₂ + 2HCl + 2HF

[0025]

CH ₃ Br + 3 / 2O ₂ → CO + HBr + H ₂ O (Chemical Formula 3) In order to carry out the decomposition reaction of the organic halogen compound having 2 carbon atoms, water is added to the gas to be treated by dissolving water vapor with respect to the organic halogen compound. It is adjusted so that the number is three times or more.
By performing the reaction in such an atmosphere, an improvement in the decomposition efficiency can be expected. It also has the advantage that the decomposition products are obtained in a form of hydrogen halide which is easy to work up. If it is less than three times, these effects are not sufficient.

It is preferable that the concentration of the organic halogen compound in the reaction gas does not exceed 10 vol%. If the concentration is higher than 10 vol%, the activity of the catalyst having a porous layer of tungsten oxide is apt to decrease. Further, when the treatment concentration increases, the amount of HF and HCl generated increases.
Problems such as corrosion of the device material also occur. Conversely, when the processing density is 10
If the concentration is as low as 00 ppm or less, the energy required for decomposition is smaller than other treatment methods, but energy loss occurs. Depending on the amount of halogen element contained in the molecule, when treating an organic halogen compound having 1 carbon atom,
An organic halogen compound concentration of 0.1 to 10 vol% is preferable, and when the number of carbon atoms is 2, 0.1 to 6 vol% is preferable.

The temperature at which the catalyst is brought into contact with the catalyst preferably does not exceed 500 ° C. When the catalyst temperature is 500 ° C. or higher, the reaction between the catalyst and F tends to proceed, and the performance of the catalyst tends to decrease. In particular, when treating an organic halogen compound having 1 carbon atom, the temperature is preferably from 250 to 450 ° C. In the case of an organic halogen compound having 2 carbon atoms, the halogen element in the molecule may increase, and the temperature is preferably 300 to 500 ° C. When an organic halogen compound is treated at a temperature exceeding 500 ° C., high-temperature gases of HF and HCl, which are decomposition products, flow in the apparatus, and the reaction tubes and pipes of the organic halogen compound processing apparatus are rapidly corroded. Progressed,
Costs such as maintenance are required.

The processing gas is applied on the catalyst at a space velocity of 50%.
It is preferably used at 0 to 100,000 / hour. When treating an organic halogen compound having 1 carbon atom, the space velocity is 1,
000 to 50,000 / hour is preferred, and when an organic halogen compound having 2 carbon atoms is treated, 500 to 10,000
/ Hour space velocity is preferred.

The shape of the reactor for carrying out the present invention can be basically a conventional fixed bed, moving bed or fluidized bed type reactor. However, as a decomposition product gas, hydrogen fluoride, hydrogen chloride or the like can be used. Since a corrosive gas is generated, a reactor that removes an acid component by contacting the decomposition product gas with an alkaline solution immediately after passing through the catalyst layer is preferable.

The processing device includes an organic halogen compound gas supply device, a water vapor supply device, an air supply device, a reactor for charging the catalyst, a heating source for heating the catalyst, a catalyst, and a washing tank for decomposition gas generated. Apparatus size and catalyst usage can be adjusted according to the compound concentration. When the organic halogen compound to be treated is liquid at room temperature, it is gasified in advance and introduced into the catalyst layer. The catalyst may be heated by an electric furnace or the like, or may be mixed with a combustion gas such as propane, kerosene, city gas, or the like, and then mixed with an organic halogen compound gas or water vapor and introduced into the catalyst layer. The material of the reactor filled with the catalyst is preferably a corrosion-resistant material such as Inconel or Hastelloy. The structure of the cracked gas cleaning tank has high efficiency of cleaning by the spray tower, and hardly causes clogging of pipes due to crystal precipitation or the like. A method of bubbling a decomposition product gas in an alkaline solution and a washing method using a packed tower are also preferable methods.
Furthermore, the entirety of these devices is loaded on a 2t truck or the like,
It is also possible to move to a collection place of discarded refrigerators, automobiles or the like, or to a place where an organic halogen compound packed cylinder is stored, extract the contained organic halogen compound, and directly treat it. Further, a circulation pump for circulating the cleaning liquid in the decomposition product gas cleaning tank and an exhaust gas adsorption tank for adsorbing carbon monoxide and the like in the exhaust gas may be simultaneously mounted.
Further, a generator, a cylinder filled with fuel such as propane, kerosene, city gas or the like serving as a heating source may be simultaneously mounted.

Since the catalyst of the present invention has a porous layer of silica holding strong acid sites and a porous layer of tungsten oxide hardly generating fluoride on the surface of titania, it exhibits high activity for organic halogen compounds. It can suppress fluorination (formation of TiOF ₂ ) of titania and shows high durability. Tungsten oxide works to improve the durability because it hardly generates fluoride, and titania and silica work to improve the decomposition rate.
Since this catalyst does not immediately deteriorate in catalytic performance unlike the conventional catalyst, an operation such as catalyst replacement is not required, and the cost of the CFC decomposition process can be reduced.

The catalyst is preferably prepared by an impregnation method.
When the impregnation method is used, a porous layer of silica or tungsten oxide is formed on the surface of porous titania grains or granulated titania grains, and alumina and tungsten oxide are uniformly formed inside the titania grains. One or more of these can be dispersed, and even when silica or tungsten oxide on the surface of the titania particles is peeled off, the titania particles have low reactivity with F, exhibit high activity and high durability.
By using the catalyst of the present invention, an organic halogen compound gas having a high concentration not exceeding 10 vol% can be efficiently treated.

Further, even if Mo and V are added as the third component to the catalyst containing titania, silica and tungsten oxide, molybdenum oxide and vanadium oxide cover the titanium oxide surface exposed by the separation of the tungsten oxide. And the durability is improved.

In addition, the presence of S increases the acidity of the reaction site in the catalyst. The strong acid point is H, which is a strong acid in the decomposition product.
It is hardly deteriorated by F and HCl.
It is effective for improving durability.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples.

Example 1 In this example, the activity of a catalyst in which the surface of titania was covered with a porous layer of silica and tungsten oxide was examined.

A granular titanium oxide having a diameter of 2 to 4 mm (CS-224S, manufactured by Sakai Chemical Co., Ltd.) was dried at 120 ° C. for 2 hours to prepare a catalyst A. 100 g of the catalyst A was impregnated with 15 g of a silica sol having a content of 20% by weight and 22.5 g of distilled water added to an aqueous sol solution B. The whole was dried at 120 ° C. for 2 hours in the air, and then kept at 500 ° C. for 2 hours. By calcining, catalyst C was produced. The amount of silica in the catalyst C was analyzed by hydrofluoric acid gravimetric analysis, and the amount of titania was analyzed by ICP emission spectroscopy. As a result, it was 1.5 wt% with respect to titania. next,
The catalyst C was impregnated with a solution D in which 41.25 g of ammonium paratungstate was dissolved in 37.5 g of an aqueous hydrogen peroxide solution. After impregnation, it was dried again at 120 ° C. for 2 hours to obtain catalyst E. This catalyst E was impregnated with the solution D again. After impregnation,
The catalyst was dried at 120 ° C. for 2 hours and calcined at 500 ° C. for 2 hours to prepare Catalyst F. The amount of tungsten oxide in Catalyst F is
When analyzed by CP emission spectroscopy, the atomic ratio of Ti: W was 80:20 mol%.

The configuration of the apparatus used in the experiment is as follows. The reaction tube is an Inconel reaction tube having an inner diameter of 31 mm, and has a catalyst layer at the center of the reaction tube. It has a thermocouple protection tube made of Inconel with an outer diameter of 3 mm inside. The reaction tube is heated in an electric furnace, and the temperature of the catalyst is measured with a thermocouple. The amount of water vapor was adjusted by supplying a predetermined amount of pure water to the upper part of the reaction tube by a pump and evaporating the same. Organic halogen compounds are C
FC12 was used. The supplied processing gas has the following composition.

CFC12 3% Water vapor 15% Oxygen 10 to 20% Nitrogen balance Gas having this composition was passed through a catalyst layer having a catalyst temperature of about 460 ° C. at a space velocity of 2,300 per hour. The decomposition product gas that passed through the catalyst layer was bubbled into an alkaline aqueous solution, and the concentration of CFC12 in the gas that passed through the alkaline aqueous solution was analyzed by FID gas chromatography. The decomposition rate of the organic halogen compound was determined by the following equation.

[0040]

(Equation 1)

FIG. 1 shows the decomposition rate of CFC12 at each reaction temperature. As a comparative example, the same method as that of the catalyst F was used, except that 100 g of the catalyst G without the addition of silica and 100 g of the catalyst A were impregnated with an aqueous sol solution B obtained by adding 32.5 g of distilled water to 5 g of a silica sol having a content of 20% by weight. Catalyst I, prepared in the same manner as Catalyst F, except that 100 g of Catalyst H and Catalyst A prepared in Example 2 were impregnated with 25 g of silica sol having a content of 20% by weight and 12.5 g of distilled water added to 25 g of silica sol. . Catalyst I is an example that deviates from the silica content of the present invention.

In the United Nations Environment Program (UNEP), CF
It is said that the CFC decomposition rate recognized as a C treatment method is 99%.

Example 2 FIG. 2 shows the results of a continuous cracking test of the catalysts F and G of the present invention at a catalyst temperature of 460 ° C. for 100 hours. The test conditions are the same as in Example 1.

Example 3 FIG. 3 shows the result of examining the decomposition activity of HCFC22 at each catalyst temperature using the catalyst F of the present invention. The test conditions are the same as in Example 1.

(Embodiment 4) This embodiment is an example of an apparatus for decomposing an organic halogen compound when the organic halogen compound to be treated is a liquid at room temperature. The disassembly device is shown in FIG.

The concentration of the CFC 12 gas 1 to be treated is measured by an analyzer 3 such as a FID gas chromatograph, and diluted with the air 2 to a Freon concentration of about 3%. After adding water vapor 4 in an amount 5 times the number of moles of Freon to the diluted Freon gas, Example 1 is introduced into the catalyst layer 5 filled with the catalyst. At this time, the space velocity is 2,300 per hour (space velocity = gas flow rate (ml / h) / catalyst amount (ml)). The catalyst layer was heated in an electric furnace 6 from the outside, and the catalyst temperature was set to 460 ° C. In addition,
As a method of raising the temperature of the catalyst, a method of flowing a high-temperature gas obtained by burning propane gas or the like can also be used. The decomposition product gas is bubbled into the alkali absorption tank 8 while being in contact with the aqueous sodium hydroxide solution sprayed from the spray nozzle 7. The gas that has passed through the alkali absorption tank 8 passes through an adsorption tank 9 filled with activated carbon or the like, and is then released to the atmosphere. In addition,
The liquid sprayed from the spray nozzle 7 may be simple water,
A slurry such as calcium carbonate may be used. The aqueous alkaline solution 10 that has become waste liquid in the alkaline absorption tank 8 can be taken out periodically and a new alkaline aqueous solution 11 can be replaced. The alkali liquid sprayed from the spray nozzle circulates the solution in the alkali absorption tank 8 by the pump 12.

(Embodiment 5) This embodiment is an example of an apparatus for decomposing an organic halogen compound when the organic halogen compound to be treated is a liquid at room temperature. The device is shown in FIG.

This is an example in which a preheater 14 is provided in the organic halogen compound decomposing apparatus of the fourth embodiment. Here, only the differences from the third embodiment will be described. Like CFC113 liquid 13,
When the organic halogen compound to be treated is liquid at room temperature, it is vaporized by the preheater 14, its concentration is measured by an analyzer 3 such as a FID gas chromatograph, etc., and diluted with air 2 to about 3% of Freon concentration. The diluted Freon gas was used in Example 4 below.
The same processing is performed.

[0049]

According to the present invention, an organic compound containing halogen such as fluorine, chlorine and bromine such as chlorofluorocarbons (CFCs), hydrofluorocarbons (alternative fluorocarbons), trichloroethylene, methyl bromide and halon is used. Decomposes with high efficiency and can maintain activity for a long time.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of the results showing the relationship between the decomposition activity of CFC12 of the catalyst of the present invention.

FIG. 2 shows a catalyst temperature of 460 ° C. and 1
Explanatory drawing of the result of having performed the continuous decomposition test of 00h.

FIG. 3 is an explanatory diagram of the results showing the relationship between the decomposition activity of HCFC22 of the catalyst of the present invention.

FIG. 4 is a system diagram of an organic halogen compound decomposing apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a system diagram of an apparatus for decomposing an organic halogen compound according to a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... CFC12 gas, 2 ... Air, 3 ... FID gas chromatograph, 4 ... Steam, 5 ... Catalyst layer, 6 ... Electric furnace, 7 ...
Spray nozzle, 8: alkali absorption tank, 9: adsorption tank, 10
... Waste liquid, 11 ... New alkaline aqueous solution, 12 ... Pump, 13
... CFC113 liquid, 14 ... Remaining heater.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Yasuda 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory, Ltd. (72) Inventor Hisao Yamashita 7-1 Omikacho, Hitachi City, Ibaraki Prefecture # 1 Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Shigeru Azuhata 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Shin Tamada, Hitachi City, Ibaraki Prefecture 3-1-1, Machi-cho Hitachi, Ltd. Hitachi Plant

Claims (3)

[Claims] 1. A method comprising the steps of: containing titania, silica and tungsten oxide, wherein said silica is 0.5% by weight or more and 2% by weight of titania;
And the titania and the tungsten oxide have an atomic ratio of Ti to W of 20 mol% or more and 95 mol or less.
% Or less, and W is 80 mol% or less and 5 mol% or more, and a catalyst in which at least the surface of the titania is substantially covered with at least one kind of porous layer of the silica and the tungsten oxide, not more than 10 vol% A method for treating an organic halogen compound by contacting a gas stream containing an organic halogen compound, wherein said gas stream is heated at a temperature not exceeding 500 ° C. and in the presence of water vapor not exceeding 30 vol% of a total gas flow rate. A process for decomposing the organic halogen compound into carbon monoxide, carbon dioxide and hydrogen halide by contacting the organic halogen compound with the organic halogen compound. 2. Titanium, silica and tungsten oxide, wherein the silica is contained in a concentration of 0.5% by weight or more and less than 2% by weight of titania, and titania and tungsten oxide are T
the atomic ratio of i to W is not less than 20 mol% and not more than 95 mol% of Ti;
An organohalogen compound decomposition catalyst, wherein W is 80 mol% or less and 5 mol% or more, and at least one porous layer of silica and tungsten oxide is provided on at least the surface of titania. 3. The method according to claim 2, wherein S, M are used as the fourth component.
A catalyst for decomposing an organic halogen compound which contains one or more elements of o and V, and wherein the ratio of each metal element is 0.001 to 10 mol% with respect to Ti atom.