JP3376789B2 - Method for treating organic halogen compounds with a catalyst - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention decomposes halogenated organic compounds such as chlorofluorocarbons (CFCs, eg, CFCs), trichloroethylene, methyl bromide, halon, etc. with a catalyst to achieve high efficiency decomposition. Regarding the method. The present invention also relates to a catalyst used in the decomposition treatment of an organic halogen compound, a method for preparing the same, and a decomposition treatment apparatus.

[0002]

2. Description of the Related Art Organohalogen compounds containing halogen such as fluorine, chlorine or bromine such as chlorofluorocarbon, trichloroethylene, methyl bromide and halon are widely used as foaming agents, refrigerants, fire extinguishing agents and fumigants. ing. However, these organic halogen compounds cause destruction of the ozone layer, and have a serious influence on the environment such as the generation of carcinogenic substances.

Under these circumstances, a method of recovering an organic halogen compound and decomposing it has been studied. Known methods for decomposing organic halogen compounds include a method using a catalyst, a method of burning at a high temperature of 800 to 900 ° C., a method of using plasma, and the like. However, among these methods, the method using combustion and plasma has a problem that energy efficiency is low because a large amount of fuel and electric power are used, and that the corrosive halogen produced damages the furnace wall. Particularly, in the plasma method, a high temperature of 6000 ° C. or more causes a large energy loss. On the other hand, the method using a catalyst is an excellent method as long as the activity of the catalyst is high because it can be processed with low energy.

As a method of using a catalyst, Japanese Patent Publication No. 6-593
No. 88 discloses a method using a catalyst containing titania. Here, a catalyst containing titania and tungsten oxide, a catalyst containing titania and vanadium oxide, and the like are described. However, the organohalogen compound to be contacted with these catalysts is limited to the gas flow containing the organohalogen compound having 1 carbon atom without any carbon-hydrogen bond, and in the case of treating CCl ₄ of ppm order also in the examples. Only the example of is shown. A catalyst containing titania and tungsten oxide uses tungsten oxide as a metal and TiO 2.
It is specified that it is contained at a concentration of about 0.1 to 20% by weight of ₂ (converted into atomic ratio, Ti is 92 mol% or more and 99.96 mol% or less, W is 8 mol% or less and 0.04 mol% or more).

The influence of organic halogen compounds as a catalyst poison is greater with fluorine than with chlorine. Therefore, it is desired to find a catalyst which has high activity not only for chlorine but also for organohalogen compounds containing fluorine, bromine and the like, and which has long-lasting activity.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an organohalogen compound with a catalyst having a high activity not only for an organic compound of chlorine but also for an organic compound of fluorine or bromine and having a long-lasting activity. The object is to provide a method of disassembling and processing.

Also provided are methods for preparing such catalysts and processing equipment used to carry out the decomposition treatment of organohalogen compounds.

[0008]

The catalyst of the present invention contains titania and tungsten oxide, and the atomic ratio of Ti and W is T.
i is 20 mol% or more and 95 mol% or less, W is 80 mol% or less and 5 mol% or more, and at least the surface of titania is covered with a porous layer of tungsten oxide.

Titanium and tungsten can be contained in the form of a mixture of oxides or a complex oxide.
Tungsten oxide is mainly contained in the form of WO ₃ .

In the present invention, the content ratio of titanium and tungsten is important in order to exhibit high activity against any of organic compounds containing halogen such as chlorine, fluorine and bromine. It is based on the finding that layers need to cover the titania.

The catalyst composed of titania and tungsten oxide disclosed in Japanese Patent Publication No. 6-59388 does not have a porous layer of tungsten oxide on the surface of titania,
Therefore, it does not show high activity against organic halogen compounds containing fluorine, bromine, etc. other than chlorine.

In the catalyst of the present invention, the porous layer of tungsten oxide may be present only on the surface of the TiO ₂ particles,
It may be present both on the surface and inside the TiO ₂ particles. Rather, it is preferably present in both. The thickness of the porous layer made of tungsten oxide is preferably 1 Å or more and 5 mm or less. If the thickness of the tungsten oxide porous layer is too thin, TiO ₂ is easily poisoned by halogen, and if it is too thick, the activity of the catalyst becomes low.

The catalyst of the present invention may contain at least one selected from sulfur, phosphorus, molybdenum and vanadium. This further enhances the durability of the catalyst.
The total content of these elements should be in the range of 0.001 to 30 mol% with respect to the titanium atom. Sulfur is included as a sulfate, phosphorus is included as a phosphate, and molybdenum and vanadium are included as oxides.

When the organic halogen compound is a molecule having 1 carbon atom, the atomic ratio of Ti to W is preferably 40 mol% or more and 90 mol% or less, and W is 60 mol% or less and 10 mol% or more. Organic halogen compound has 2 carbon atoms
If the number of halogen elements contained in the molecule is large, the atomic ratio of Ti to W is 20%.
15 mol or more and 85 mol% or less, W 80 mol% or less
It is preferable to increase the porous thickness of WO ₃ covering the surface of the TiO ₂ particles to be 1% or more.

The catalyst of the present invention can be used after being formed into a granular shape, a pellet shape, a honeycomb shape or the like. As a molding method, an extrusion molding method, a tablet molding method, a rolling granulation method, or the like can be applied. In this case, in order to improve the strength of the catalyst or increase the specific surface area, alumina cement,
Binders such as calcium-sodium cement, other ceramics or organic components can be mixed.

The catalyst of the present invention can be used by supporting it on a granular carrier such as alumina or silica by a method such as impregnation. Further, the catalyst of the present invention or a granular carrier such as alumina or silica carrying the catalyst of the present invention may be used by coating it on a honeycomb or plate made of ceramics or metal.

The method for decomposing an organohalogen compound of the present invention is to bring a gas stream containing an organohalogen compound into contact with the above catalyst at a temperature of 200 to 500 ° C. in the presence of water vapor. Thereby, the organic halogen compound is
Decomposes into carbon dioxide and hydrogen halide, or carbon monoxide and carbon dioxide and hydrogen halide. When the organic halogen compound is CFC113, it is decomposed into carbon monoxide, carbon dioxide and hydrogen halide. When the organic halogen compounds are CFC11 and CFC12, they are decomposed into carbon dioxide and hydrogen halide. According to the treatment method of the present invention, the deterioration of the catalyst due to the halogen contained in the decomposition product of the organic halogen compound is small, and the catalyst maintains a high activity for a long time.

In contacting the gas stream containing the organohalogen compound with the catalyst, it is preferable that the content of the organohalogen compound in the gas stream does not exceed 30 vol%. When the concentration of the organohalogen compound in the gas stream is high, the decomposition rate of the organohalogen compound is low, and the organohalogen compound may be discharged as it is without being decomposed. The lower limit of the amount of organohalogen compound in the gas stream is 1
It is desirable not to fall below 000ppm. When the organic halogen compound has a low concentration of 1000 ppm or less, energy loss occurs although the energy required for decomposing the organic halogen compound is small.

When treating an organic halogen compound having 1 carbon atom, the concentration of the organic halogen compound is particularly 0.1 to 3.
The range of 0 vol% is preferable, and when treating an organic halogen compound having 2 carbon atoms, the concentration of the organic halogen compound is particularly preferably in the range of 0.1 to 10 vol%. In order to adjust the concentration of the organic halogen compound, it is desirable to add air or the like when the organic halogen compound is recovered.

The amount of water vapor is an effective amount required for decomposing the organic halogen compound. For example, in the case of decomposing an organic halogen compound having 2 carbon atoms, it is preferable that the gas flow contains 3 times or more moles of water vapor as compared with the organic halogen compound.

As the method for preparing the catalyst according to the present invention, W
Impregnate a TiO ₂ grain with a solution containing
An impregnation method of converting to O ₃ , a method of applying a solution containing W to TiO ₂ grains, a method of vapor deposition, or the like can be applied.

In the case of the impregnation method, each fine TiO ₂ particle is coated with W ions, and the uniformity is excellent. When the amount of tungsten oxide is large, W ions are also coated on the surface of the TiO ₂ granulated particles formed by assembling each fine TiO ₂ particle.

When the catalyst is prepared by the impregnation method,
The atomic ratio of Ti and W is such that Ti is 20 mol% or more and 90 mol% or more.
Hereinafter, W should be 80 mol% or less and 10 mol% or more. In the case of the impregnation method, if the atomic percentage of W with respect to Ti does not exceed 10 mol%, the surface of the TiO ₂ particles will be W.
Not covered by a porous layer of O ₃ . When the surface of the TiO ₂ particles are not covered by a porous layer of WO _3, TiO ₂
Poisoning due to halogen occurs from the exposed surface of the particle, and for example, TiOF ₂ is generated in the exposed part of the TiO ₂ particle, and the activity of the catalyst gradually decreases.

When the catalyst is prepared by a vapor deposition method or a coating method, a WO ₃ porous layer can be formed on the surface of the TiO ₂ particles even if the atomic ratio of W is as small as about 5 mol%.

In the catalyst preparation method of the present invention, it is desirable to prepare the catalyst using TiO ₂ particles obtained by granulation. The particles obtained by granulation are those obtained by once crushing the raw material particles and then compression-molding with a press or the like, then crushing again and selecting to a desired particle size by sieving. The size is almost uniform and it is easy to adjust the amount of holes. The rolling granulation method is most preferable as the granulation method.

As the titanium raw material for preparing the catalyst of the present invention, in addition to titanium oxide, various compounds which produce titanium oxide by heating can be used.

Water, ammonia water, or an alkaline solution is added to a titanium material such as titanic acid, titanium sulfate, titanium chloride, or an organic titanium compound to form a hydroxide precipitate, which is finally calcined to form titania. The method is also one of the effective methods.

As the tungsten raw material, tungsten oxide, tungstic acid, ammonium paratungstate, or the like can be used. It is also possible to use a raw material containing both phosphorus and tungsten, such as ammonium phosphotungstate. The more acidic the active sites in the catalyst, the less likely the catalyst of the present invention is to deteriorate. Therefore, it is desirable that the catalyst contains components such as S and P that enhance the catalytic acidity. S is present in the form of oxide ions such as sulfate ions.

Even a catalyst composed of TiO ₂ initially has a high activity for decomposing organic halogen compounds. However, when the organic halogen compound is an organic compound of fluorine, TiOF ₂ is generated and desorbed from the catalyst, the active sites are decreased, and the activity is gradually decreased. On the other hand, tungsten oxide hardly reacts with fluorine. Therefore, by covering the surface of TiO _{2 with} a porous layer made of tungsten oxide, poisoning of TiO ₂ by fluorine can be prevented. Further, at the interface between TiO ₂ and tungsten oxide WO ₃ , a strongly acidic new active site which is hardly deteriorated by fluorine is developed.

Tungsten oxide WO ₃ has a smaller specific surface area than TiO ₂ , and it is not effective to prepare a catalyst only with tungsten oxide.

The organic halogen compound to be treated in the present invention is a compound containing at least one of fluorine, chlorine and bromine in the organic compound, and for example, various chlorofluorocarbons (fluorocarbons), trichloroethylene, methyl bromide, etc. Is.

Taking Freon 113 and methyl bromide as an example,
A typical reaction formula of the organic halogen compound decomposition treatment method of the present invention is shown below.

C ₂ Cl ₃ F ₃ + 3H ₂ O → CO + CO ₂ +3
HCl + 3HF CH ₃ Br + 3 / 2O ₂ → CO + HBr + H ₂ O As is clear from these reaction formulas, when the decomposition reaction of the organic halogen compound having 2 carbon atoms is carried out, the molar amount of the organic halogen compound relative to the organic halogen compound is changed in the gas to be treated. It is necessary to keep water vapor in excess of three times.

The temperature at which the gas stream containing the organohalogen compound is brought into contact with the catalyst, that is, the reaction temperature, is preferably in the range of 200 to 500 ° C. For this purpose, it is preferred to heat the gas stream containing the organohalogen compound or to heat the reactor containing the catalyst. When the reaction temperature exceeds 500 ° C., the reaction between the catalyst and fluorine starts to proceed and the activity of the catalyst gradually decreases. When treating an organic halogen compound having 1 carbon atom, the reaction temperature is 250 to 45.
0 ° C. is particularly preferred. In addition, the reaction temperature when treating an organic halogen compound having 2 carbon atoms is particularly preferably 300 to 500 ° C.

The contact time of the gas stream containing the organohalogen compound with the catalyst may be very short, and about 1 second is sufficient to decompose the organohalogen compound. Therefore, the space velocity per hour can be changed in a wide range of 500 to 100,000 / hour. The space velocity when treating an organohalogen compound having 1 carbon atom is 1,000 to
50,000 / hour is particularly preferable, and the space velocity when treating an organic halogen compound having 2 carbon atoms is 500 to 1
Especially preferred is 0000 / hour.

The reactor used for carrying out the treatment method of the present invention may be a normal fixed bed, moving bed or fluidized bed type reactor, but as a decomposition product gas, a corrosive gas such as HF and HCl. Therefore, the reactor should be made of a material that is not easily damaged by these corrosive gases.

The treatment apparatus used for carrying out the treatment method of the present invention includes, in addition to the above-mentioned reactor, means for adjusting the concentration of the organohalogen compound in the gas stream, for example, air is supplied to the gas stream. Means for heating at least one of the organohalogen compound-containing gas stream and the catalyst for contacting the catalyst at a reaction temperature of 200 to 500 ° C., and an amount of water effective for decomposing the organohalogen compound in the gas stream. And an alkali cleaning tank for neutralizing a part of carbon dioxide, which is a decomposition product of the organic halogen compound, and halogen hydrogen by cleaning the gas flow passing through the catalyst layer with an alkaline aqueous solution. It is more preferable to provide a means for adsorbing carbon monoxide, which is a decomposition product of an organic halogen compound, at the latter stage of the alkali cleaning tank.

When the organic halogen compound is liquid at room temperature, it is gasified in advance and introduced into the catalyst layer. As a method of heating the catalyst, an electric furnace may be used, or a combustion gas such as propane, kerosene, and city gas may be mixed with an organic halogen compound gas,
Steam may be mixed and introduced into the catalyst layer. As a material for the reactor filled with the catalyst, a corrosion resistant material such as Inconel or Hastelloy is preferable. As the structure of the alkali cleaning tank, a structure in which an alkali solution is sprayed for cleaning is highly efficient, and it is preferable that the piping is not clogged due to crystal precipitation or the like. A method of bubbling the decomposition product gas in the alkaline solution or a method of cleaning using a packed tower may be used.

The decomposition processing apparatus of the present invention may be carried on a truck or the like. The place to carry
For example, a collection place for discarded refrigerators, cars, etc.
It is a storage place for a cylinder filled with an organic halogen compound.

In the treatment method of the present invention, since there is almost no deterioration of the catalyst, the replacement operation of the catalyst is unnecessary or almost unnecessary.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

Example 1 In this example, the catalyst activity of the catalyst prepared by the impregnation method will be described when the ratio of Ti and W is changed or the type of gas to be treated is changed.

[Experiment 1] The atomic ratio of Ti and W was 8: 2 (mol
%) And a comparative catalyst in which the atomic ratio of Ti and W is 9.5: 0.5 (mol%).
The catalytic activity was compared by decomposing an organohalogen compound composed of C12.

In the catalyst of the present invention, granular titanium oxide having a diameter of 2 to 3 mm (CS-224, manufactured by Sakai Chemical Industry Co., Ltd.) is crushed and sieved to a particle size of 0.5 to 1 mm, and then at 120 ° C. After drying for an hour, 100 g of this titanium oxide was impregnated with a hydrogen peroxide solution in which 82.2 g of ammonium paratungstate was dissolved, and dried again at 120 ° C. for 2 hours, and then 500
It was prepared by firing for 2 hours at ℃.

In order to analyze the cross section of the catalyst, the catalyst was fixed in a resin containing an epoxy resin as a main component. The cross section of the catalyst was taken by scanning electron microscope (SEM).
As a result of observing with py), it was confirmed that a white layer was present at the interface between the catalyst particles and the resin, and this white layer was confirmed to be the W component by an electron probe microanalyzer. The thickness of the white layer was approximately 10 ⁵ Å. As a result of analysis, this catalyst was found to have an atomic ratio of Ti to W of 8: 2 (mol
%), And the S component was contained in an amount of 6.9 mol% with respect to Ti atoms. It was confirmed that the S component was contained in the form of sulfate.

Comparative example catalysts were prepared by using titanium oxide 10
Ammonium paratungstate 17.3 for 0 g
The procedure is exactly the same as the method for preparing the catalyst of the present invention, except that it is impregnated with hydrogen peroxide solution in which g is dissolved. The comparative catalyst is
The atomic ratio of Ti and W was 9.5: 0.5 (mol%), and the S component was contained at 6.9 mol% with respect to Ti atoms. The S component was sulfate. When a cross section of this catalyst of Comparative Example was observed with a scanning electron microscope, no white layer was observed. Since the amount of tungsten oxide is small, the tungsten oxide exists only inside the titania particles, and the tungsten oxide does not appear on the surface of the titania.

The decomposition treatment experiment of the organic halogen compound CFC12 was carried out as follows. First, the inner diameter of the reaction tube is 1
A 6 mm Inconel reaction tube was used, a catalyst layer was arranged in the center of the reaction tube, and an Inconel thermocouple protection tube having an outer diameter of 3 mm was provided inside the reaction tube. Then, the catalyst temperature was measured with a thermocouple during the decomposition process. The reaction tube was heated in an electric furnace. The amount of water vapor was adjusted by supplying a predetermined amount of pure water to the upper part of the reaction tube with a pump and evaporating it.

The composition of the gas to be treated is as follows.

CFC12 3 vol% Water vapor 15 vol% Oxygen 10-20 vol% Nitrogen Remaining gas to be treated having the above composition is supplied to the reaction tube, and the decomposition product gas passing through the catalyst layer is bubbled in the alkaline aqueous solution and passed through the alkaline aqueous solution. CFC12 concentration in the gas
ID (abbreviation of Flame Ionization Detector) was analyzed by a gas chromatograph. The space velocity of the gas was 3,000 / hour, and the temperature of the catalyst layer in the reaction tube was 440 ° C. The decomposition rate of the organic halogen compound was calculated by the following formula.

[0050]

[Equation 1]

FIG. 1 shows the fluctuations in the activity of the catalyst of the present invention and the catalyst of the comparative example when they were continuously tested for 500 hours. The horizontal axis of FIG. 1 represents the reaction time, and the vertical axis represents the decomposition rate of the organic halogen compound. The catalyst of the present invention did not show a decrease in activity during the continuous test for 500 hours, but the catalyst of the comparative example showed a decrease in activity after 200 hours. In the reaction tube in which the comparative catalyst was arranged, precipitation of TiOF ₂ was observed at the decomposition product gas outlet at the lower part of the reaction tube.

[Experiment 2] In this experiment, for the catalyst of the present invention prepared in Experiment 1, the gas to be treated was CFC1 having 2 carbon atoms.
The catalyst activity was investigated by changing to 13. The results are shown in FIG. The test conditions are exactly the same as in Experiment 1. However, 100
It was a continuous test of time. The catalyst of the present invention also showed high activity against the decomposition treatment of CFC113.

[Experiment 3] In this experiment, the catalytic activity in the decomposition treatment of CFC12 was examined by changing the atomic ratio of Ti and W. The method for preparing the catalyst is exactly the same as in Experiment 1. The concentration of CFC12 was 6 vol%, which was higher than that in Experiment 1. The other test conditions were the same as in Example 1.

FIG. 3 shows the content ratio of Ti and W and CFC12.
It shows the relationship with the decomposition rate of. Decomposition rate is the reaction start 2
The value after hours. All the catalysts of the present invention having a W content in the range of 10 to 80 mol% exhibit a high decomposition rate of 99% or more. According to the United Nations Environment Program (UNEP), the CFC decomposition rate recognized as a CFC treatment method is said to be 99%, and the catalyst of the present invention satisfies that condition.

By changing the W content ratio, the thickness of the porous layer made of WO ₃ also changes. Therefore, in FIG.
The relationship between the thickness of the O ₃ porous layer and the decomposition rate of the organic halogen compound is shown. The decomposition rate is a value two hours after the start of the reaction as in FIG.

[Experiment 4] In this experiment, with respect to the catalyst of the present invention prepared in Experiment 1, the gas to be treated was changed to CFC11 to examine the catalytic activity. The composition of the gas to be treated is CFC11.
Is 3vol%. The test conditions are exactly the same as in Experiment 1 except that a continuous test of 20 hours is performed.

The results are shown in FIG. The decomposition rate of CFC11 reached 99.9%, and no decrease in catalytic activity was observed.

[Experiment 5] In this experiment, the catalyst of the present invention prepared in Experiment 1 was tested by changing the concentration of the gas to be treated. The components of the gas to be treated were the same as in Experiment 1, and the concentration of CFC12 was changed within the range of 1 to 10 vol%.

FIG. 6 shows the relationship between the concentration of CFC12 and the decomposition rate. The decomposition rate is a value one hour after the start of the reaction. C
The decomposition rate of FC12 tends to decrease as the concentration of CFC12 in the process gas increases. The catalyst of the present invention has a CFC of 12 when the space velocity is 3,000 / hour.
Shows a high decomposition rate of 99% or more in the range in which the concentration does not exceed 10 vol%.

[Experiment 6] In this experiment, with respect to the catalyst of the present invention prepared in Experiment 1, the reaction temperatures were 440 ° C. and 600 ° C.
The catalytic activity was examined by changing the two types. In addition, the experiment is C
Two tests were performed for each of FC11 and CFC12. The concentrations of CFC11 and CFC12 were both 3 vol%. The other test conditions are the same as those in Experiment 1. The results are shown in Fig. 7. The decomposition rate is a value one hour after the start of the reaction. When the reaction temperature was 440 ° C., the catalyst activity did not decrease during the 100-hour continuous test, but when the reaction temperature was 600 ° C., the catalyst activity decreased with the elapse of the reaction time.

Example 2 In this example, the catalytic activity was examined when the TiO ₂ raw material or the tungsten raw material was changed and the catalyst preparation method was changed. CFC1 for disassembly
I went to 2.

The experimental method and the composition of the gas to be treated are the same as in Experiment 1. However, the experiment was a continuous treatment for 10 hours.

[Experiment 7] In this experiment, the catalytic activity when TiO ₂ grains were changed was examined. Specifically, the diameter is 0.
5 to 1 mm commercially available granular titanium oxide (CS-3 manufactured by Sakai Chemical Co., Ltd.
00) is dried at 120 ° C for 2 hours, and this titanium oxide 100
Ammonium paratungstate 82.2 for g
It was impregnated with hydrogen peroxide solution in which g was dissolved. After impregnation, it was dried again at 120 ° C. for 2 hours and calcined at 500 ° C. for 2 hours to prepare a catalyst. The decomposition rate of CFC12 by this catalyst is shown in FIG. As in Experiment 1, the smaller the particle size and the more uniform the particle size, the higher the decomposition rate, but the difference is not so large.

[Experiment 8] In this experiment, the granulated T
The catalytic activity was investigated when the catalyst was prepared using iO ₂ grains.

The titania used as a raw material was granular titanium oxide (CS-224, manufactured by Sakai Chemical Industry Co., Ltd.) having a diameter of 2 to 3 mm, which was finely pulverized in an automatic mortar to a size of 0.5 mm or less.
It was dried for an hour and calcined at 500 ° C. for 2 hours. Next, it was put into a mold and compression-molded at a pressure of 500 kgf / cm ² . In addition,
The pressure for compression molding is preferably 250 to 3000 kgf / cm ² . This molded product was crushed and sieved to granulate titanium oxide having a particle size of 0.5 to 1 mm. TiO ₂ grains obtained 10
Ammonium paratungstate 82.
The solution was impregnated with hydrogen peroxide solution having 2 g dissolved therein. After impregnation, it was dried again at 120 ° C. for 2 hours and calcined at 500 ° C. for 2 hours. As a result of component analysis of the cross section of this catalyst by SEM analysis and electron probe microanalyzer, a porous layer of WO ₃ was confirmed on the surface of TiO ₂ grains.

The relationship between the decomposition rate of CFC12 and the reaction time is shown in FIG. The one in which the titania particles obtained by granulation are used as the catalyst raw material has a relatively small variation in the decomposition rate with the passage of reaction time and is suitable as the catalyst raw material.

[Experiment 9] Also in this experiment, the catalyst activity was investigated when a catalyst was prepared using TiO ₂ particles obtained by granulation. The granulation method is different from Experiment 8. Specifically, granular titanium oxide having a diameter of 2 to 3 mm (made by Sakai Chemical Co., Ltd., CS-22
4) was finely pulverized in an automatic mortar and dried at 120 ° C. for 2 hours. 100 g of this dry titanium oxide powder and 41.1 g of ammonium paratungstate were thoroughly mixed using a raker machine while adding distilled water. The obtained slurry was dried at 150 ° C. for 2 hours and then calcined at 500 ° C. for 2 hours. The obtained powder was put in a mold and compression-molded at a pressure of 500 kgf / cm ² . The molded product was crushed and sieved to form titanium oxide having a particle size of 0.5 to 1 mm. 100 g of the obtained titanium oxide particles were impregnated with hydrogen peroxide solution in which 41.1 g of ammonium paratungstate was dissolved.
After impregnation, it was dried again at 120 ° C. for 2 hours and calcined at 500 ° C. for 2 hours to prepare a catalyst.

As a result of component analysis of the cross section of the catalyst by SEM analysis and electron probe microanalyzer, a porous layer of WO ₃ was confirmed on the surface of the titanium oxide particles. CFC
The relationship between the decomposition rate of No. 12 and the reaction time is shown in FIG. Again, it was confirmed that the titanium oxide particles obtained by granulation were suitable as a catalyst raw material.

[Experiment 10] In this experiment, in Experiment 9, the titanium oxide particles were impregnated with hydrogen peroxide solution in which ammonium paratungstate was dissolved, but the titanium oxide dry powder and ammonium paratungstate were peroxidized. The catalytic activity was examined when the method was changed to a method of mixing while adding hydrogen. By using hydrogen peroxide, tungsten can be dispersed more highly.

The decomposition rate of CFC12 by this catalyst is shown in FIG.
Shown in 1.

[Experiment 11] In this experiment, the catalyst activity was examined by changing the impregnation method as in Experiment 1.

Ammonium paratungstate 82.2
Titanium oxide particles 100 in hydrogen peroxide water in which g is dissolved
g, then dry for 2 hours at 120 ℃, 500 ℃
The mixture was calcined for 2 hours to prepare a catalyst. CF by this catalyst
The decomposition rate of C12 is 99.9% after 50 hours from the start of the reaction.
Met.

[Experiment 12] In this experiment, the catalytic activity was examined when the tungsten raw material was changed.

The catalyst was titanium oxide 100 used in Experiment 1.
per g, impregnated with hydrogen peroxide solution in which 75.6 g of phosphotungstic acid was dissolved, dried at 120 ° C. for 2 hours, and
It was prepared by firing at 0 ° C. for 2 hours. CFC12
The decomposition rate was 99.9% 50 hours after the start of the reaction.

[Experiment 13] In this experiment, the catalyst activity was examined when the catalyst contained sulfur.

100 g of titanium oxide used in Experiment 1 was impregnated with hydrogen peroxide solution in which 82.2 g of ammonium paratungstate was dissolved, and dried at 120 ° C. for 2 hours. Then, impregnate with 75 g of 0.1% sulfuric acid and re-inject 120
A catalyst was prepared by drying at 0 ° C for 2 hours and calcining at 500 ° C for 2 hours. The decomposition rate of CFC12 was 99.9% 50 hours after the start of the reaction.

(Embodiment 3) In this embodiment, a processing apparatus for carrying out the method for decomposing an organohalogen compound according to the present invention will be described with reference to FIG.

Organohalogen compound gas (here, CFC12) 1 collected from a waste refrigerator or a waste car is FI.
The concentration is measured by an analyzer 3 such as a D gas chromatograph, and diluted with air 2 to a fluorocarbon concentration of about 3 vol%. 5 times the number of moles of fluorocarbons in the diluted fluorocarbon gas 4
After the addition of, the catalyst is introduced into the reaction tube 20 equipped with the catalyst layer 5 filled with the catalyst of the present invention. Space velocity at this time is 5.0
It is 00-100,000 / hour (space velocity = gas flow rate (ml / h) / catalyst amount (ml)). The catalyst layer 5 is heated in the electric furnace 6 from the outside. The method of raising the temperature of the catalyst may be a method of flowing a high temperature gas obtained by burning propane gas or the like into the reaction tube. The decomposition product gas of the organic halogen compound 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 the adsorption tank 9 that is filled with activated carbon and the like, and then is released into the atmosphere. The liquid sprayed from the spray nozzle 7 may be simple water or a slurry liquid such as calcium carbonate. The waste alkali solution 10 in the alkali absorption tank 8 is periodically taken out and replaced with a new alkali solution 11. The alkaline liquid sprayed from the spray nozzle is used by circulating the solution in the alkaline absorption tank 8 with the pump 12.

(Embodiment 4) This embodiment relates to a processing apparatus when an organic halogen compound is a liquid at room temperature, and FIG.
3 will be used for the explanation.

In this processing apparatus, a preheater 14 is further provided in the organic halogen compound decomposing apparatus of the third embodiment. When the organic halogen compound is liquid at room temperature like CFC113 liquid 13, it is vaporized by the preheater 14. Then, the concentration is measured by an analyzer 3 such as an FID gas chromatograph, and diluted with air 2 to a fluorocarbon concentration of about 3 vol%. After that, the same processing as that described in the third embodiment is performed.

[0081]

According to the present invention, chlorofluorocarbons (CFCs), trichloroethylene, methyl bromide,
An organic compound containing halogen such as fluorine, chlorine and bromine, such as halon, can be decomposed with high efficiency and the activity of the catalyst can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 2 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 3 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the tungsten content.

FIG. 4 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the WO ₃ porous layer thickness.

FIG. 5 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 6 is a graph showing the relationship between the decomposition rate of CFC12 and the concentration of CFC12.

FIG. 7 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 8 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 9 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 10 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 11 is a graph showing the relationship between the decomposition rate of an organic halogen compound and the reaction time.

FIG. 12 is a schematic configuration diagram of an organohalogen compound decomposing apparatus for carrying out the method of the present invention.

FIG. 13 is a schematic configuration diagram showing another embodiment of the organic halogen compound decomposing apparatus.

[Explanation of symbols]

1 ... CFC12 gas, 2 ... Air, 4 ... Steam, 5 ... Catalyst layer, 6 ... Electric furnace, 7 ... Spray nozzle, 8 ... Alkali absorption tank, 9 ... Adsorption tank, 14 ... Preheater, 20 ... Reaction tube.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B01J 27/188 B01D 53/34 135A (72) Inventor Toshiaki Arato 7-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Toshio Yamashita 1-1-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Shigeru Shodohata 1-1-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor, Shin Tamada, 3-1-1, Sachimachi, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Plant (56) Reference JP-A-3-106419 (JP, A) JP 4-122419 (JP, A) JP-A-51-11065 (JP, A) Special Table 4-501380 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 53 / 86 B01D 53/62 B01D 53/46 B01J 21/00-38/74

Claims (8)

(57) [Claims] 1. A method of decomposing an organohalogen compound by contacting a gas stream containing the organohalogen compound with a catalyst in the presence of water vapor, the gas stream comprising titania and tungsten oxide, comprising Ti and W. Atomic ratio is 20 mol of Ti
% Or more and 90 mol% or less, W is 80 mol% or less and 10 mol% or more, and at least the surface of titania is contacted with a catalyst covered with a porous layer of tungsten oxide at a temperature of 200 to 500 ° C. A method for treating an organic halogen compound. 2. The organohalogen compound according to claim 1, wherein the gas stream containing the organohalogen compound in an amount not exceeding 30 vol% is contacted with the catalyst in the presence of an effective amount of steam. Processing method. 3. A catalyst used for cracking a gas stream containing an organohalogen compound in the presence of water vapor.
It contains titania and tungsten oxide, and the atomic ratio of Ti and W is 20 mol% or more and 90 mol% or less, and W is 80 mol.
% Or less and 10 mol% or more, and at least the surface of titania is covered with a porous layer of tungsten oxide, which is an organohalogen compound decomposition catalyst. 4. The catalyst for decomposing organohalogen compounds according to claim 3, wherein the porous layer made of tungsten oxide has a thickness of 1 Å or more and 5 mm or less. 5. A method for preparing a catalyst used in the decomposition treatment of an organic halogen compound, wherein Ti and W are in an atomic ratio of 20 mol% or more and 90 mol% or less, and W is 80 mol.
% Or less comprising 10 mol% or more, the solution containing the W component from the TiO ₂ particle surface was impregnated inside the TiO ₂ particles and baking was prepared by converting the W in WO _3, tungsten oxide at least the surface of the titania A method for preparing an organohalogen compound decomposition catalyst, characterized in that it is covered with a porous layer of. 6. The method for preparing an organohalogen compound decomposition catalyst according to claim 5 , wherein the solution containing the W component is a hydrogen peroxide solution. 7. A treatment apparatus used for carrying out a catalytic decomposition method of an organohalogen compound, comprising: a reactor filled with a catalyst; and an organohalogen compound-containing gas stream introduced into the reactor. A heating means for bringing the gas flow and the catalyst into contact with each other at a temperature of 200 to 500 ° C., and an effective amount of water for decomposing the organohalogen compound is added to the gas flow. And a part of carbon dioxide in the decomposition product and halogen by washing an organic halogen compound decomposition product generated by contacting the catalyst filled in the reactor with the gas flow. comprising an alkali cleaning bath to neutralize the hydrogen, as the catalyst, comprising titania and tungsten oxide, the atomic ratio of Ti and W is, Ti is 20 mol% or more <br/> on 90 mol% or less, Is at 80 mol% or less 10 mol% or more, the organic halogen compound decomposing device characterized by comprising a catalyst surface of at least the titania is covered with a porous layer of tungsten oxide. 8. The organohalogen compound according to claim 7 , further comprising a means for adsorbing carbon monoxide in the decomposition product which has not been neutralized by alkali cleaning, at a stage subsequent to the alkali cleaning tank. Decomposition equipment.