JPH0663177A - Method of decomposing organic halogenated compound - Google Patents

Abstract

PURPOSE:To greatly enhance the decomposition efficiency for an organic halogenated compound and to enable recycling of a solvent by irradiating the organic halogenated compound with ultraviolet ray in a liquid phase under an atmosphere such that substantially no alkali is present, and by processing a product with an alkali so as to remove the same. CONSTITUTION:A device for decomposing an organic halogenated compound is composed of a decomposing tank 1, and an ultraviolet lamp 3. A suitable quantity of a reaction liquid (organic halogenated compound) 1a which is set in liquid phase by use of alcohol as a solvent is poured into the tank. That is, for example, an isopropyl alcohol solution containing CFC-11 or the like as the organic halogenated compound 1a is poured into the tank 1, and is then irradiated with ultraviolet ray from the ultraviolet lamp 3 so as to be decomposed. Then, a caustic soda aqueous solution which is alkali is added so as to deposit a salt which is then filtered. Since an alkali is added to the solution after irradiation of ultraviolet ray, so as to remove a halogen in the form of salt, alcohol as a solvent can be used again. Thereby it is possible to enable continuous process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing a halogen-based organic compound with ultraviolet rays, and more particularly, a halogen-based organic compound which is decomposed to be harmless by being irradiated with ultraviolet rays in a liquid phase. Regarding the disassembly method of.

[0002]

2. Description of the Related Art Conventionally, halogenated organic compounds have been widely used in various fields such as the chemical industry. However,
In recent years, organochlorine compounds such as trichlorethylene and P
CB (polychlorobiphenyl) has been shown to be toxic to the human body, and fluorocarbons and other so-called fluorocarbons, which are so-called CFCs, are directly harmless to the human body, but destroy the ozone layer and worsen the global environment. It has been revealed that For this reason, various methods for decomposing the halogen-based organic compound to render it harmless have been studied, but a technique completed to the stage of practical use is not yet known.

Specifically, as a method for detoxifying a halogen compound in a liquid phase, methods such as a catalytic method, an electron beam method, and a sodium decomposition method have been studied. this house,
The catalytic method is easy to operate and requires less energy, so it is highly economical, but the decomposition efficiency is low due to the low oxygen concentration in the liquid phase, and the halogen compound newly generated during decomposition produces a catalyst. However, there is a problem of rapid deterioration.

Further, the decomposition efficiency is low even in the electron beam decomposition method using ultraviolet rays and the like, and only by this electron beam method, the progress of the decomposition is hindered by the products produced during the decomposition, and the halogen-based organic compound is completely removed. It is difficult to decompose into. In addition, there is a drawback that the device becomes large, and the danger that the device is corroded by a halogen compound generated at the time of decomposition is greater than that of other methods.

Further, the sodium decomposition method has a high decomposition efficiency, but is not economical because it consumes a large amount of sodium, and has the drawback that the size of the apparatus becomes large due to safety measures for handling sodium.

Among them, the most probable ultraviolet decomposition method is the one which has hitherto been decomposed by dissolving a halogenated organic compound such as CFC in an alcohol solvent containing an alkali and then irradiating it with ultraviolet rays in order to increase the decomposition rate. Was going to do. As a result, the C-Cl bond of Freon is weakened by the electron-withdrawing effect of the OH group of the alcohol solvent, and the solvation effect of the alcohol solvent enables decomposition in the liquid phase with lower energy of ultraviolet light than in the gas phase, resulting in a decomposition rate. At the same time, the halogen compound formed during decomposition can be removed from the reaction system in the form of a salt by addition of an alkali, so that the reaction can be continued. Decomposition of many halogenated organic compounds was confirmed by this method, and the effect was recognized.

[0007]

However, in the above-mentioned conventional UV decomposition method, a decomposition product of a halogen compound such as an aldehyde generated by UV irradiation is called an aldol condensation with an alcohol in the presence of an alkali. This may adversely affect the continuation of the decomposition reaction because it causes a reaction. For this reason, the operating conditions that can be disassembled are narrow and the practicality is poor.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for decomposing a halogenated organic compound, which has a greatly improved decomposition performance in the ultraviolet decomposition method.

[0009]

In order to achieve the above object, the first invention of the present application comprises a first step of irradiating a halogenated organic compound in a liquid phase state with ultraviolet rays in an environment in which almost no alkali exists. A second step of treating the product generated by this irradiation with an alkali to remove the product.

In the second invention of the present application, the first step of irradiating the halogen-based organic compound in the liquid phase state with ultraviolet rays and the necessary and sufficient amount of alkali are added to the product produced by this irradiation. Second to produce salt and remove the product
And a step of performing the first step again in an environment in which the product and alkali hardly exist after the second step.

[0011]

As described above, in the method for decomposing a halogenated organic compound according to the first aspect of the present invention, the first step of irradiating the halogenated organic compound in a liquid phase with ultraviolet rays is performed in an environment where almost no alkali exists. This makes it possible to eliminate the influence of alkali when the halogen-based organic compound is decomposed. Then, in the subsequent second step, the halogen-based organic compound is decomposed by the irradiation of the ultraviolet rays, and the generated product is treated with an alkali to be removed, so that the progress of the decomposition may be hindered by the product. It is prevented, and the disassembling process can be repeated.

In the method for decomposing a halogen-based organic compound according to the second aspect of the present invention, the halogen-based organic compound in a liquid phase is irradiated with ultraviolet rays to the product produced in the first step,
In the step (1), a sufficient amount of alkali necessary to remove the product is added to form a salt, and the salt is removed. This makes it possible to form an environment in which the product and the alkali are scarcely present even after the second step. Therefore, when the first step is performed again, the decomposition can be performed in an environment in which almost no alkali exists, the decomposition efficiency can be significantly improved, and the solvent can be recycled.

[0013]

EXAMPLES First, a method for decomposing a halogenated organic compound according to the present invention will be described. The decomposition method of the present invention comprises a first step of irradiating with ultraviolet light and a second step of treating the solution to be decomposed after irradiation with an alkali to generate a salt. In the conventional method, a decomposition product generated by irradiation of ultraviolet rays contained in the liquid to be decomposed may cause a polymerization reaction in the presence of an alkali, which may adversely affect the decomposition reaction.

Therefore, in the present invention, the unnecessary step due to the coexistence of alkali in the ultraviolet decomposition step is prevented by separating the ultraviolet decomposition step into the first step and the decomposition step halogen with the second step. I chose Also,
At this time, as the decomposition reaction proceeds, halogen is generated and the solution becomes acidic, but there is no adverse effect on the decomposition.

However, since the amount of CFCs that can be completely decomposed is about 1/30 of the amount of the solvent, the alcohol of the solvent is reused by adding an alkali to the solution after ultraviolet irradiation to remove the halogen in the form of a salt. it can. Therefore, continuous treatment becomes possible by repeating the ultraviolet irradiation step and the alkali addition dechlorination step.

Further, any kind of alkali can be used as long as it can precipitate and separate halogen in the form of a salt, but sodium and potassium showed good performance. Sodium is the most suitable in terms of availability and price. The addition method can be in the form of an aqueous alkaline solution. Although there is no influence of the concentration of the aqueous solution, it is preferable that the concentration is as high as possible for solid-liquid separation of the salt, but about 15 N is the best from the viewpoint of handling. The amount of alkali added is preferably the same stoichiometric amount as that of halogen produced by CFC decomposition.

It is also possible to install solid alkali hydroxide in a layered form and to pass the layer to remove the halogen. Further, the salt formed needs to be solid-liquid separated and removed outside the reaction system. The method of separation and removal is not particularly limited to natural sedimentation, filtration, centrifugation, etc. However, since naturally produced salt has a large particle size, natural sedimentation is sufficient.

The solvent used is Japanese Patent Application No. 4-7100.
Isopropyl alcohol is optimal as detailed in Section 6.

Next, an embodiment according to the present invention will be described with reference to the drawings. First, the configuration of Example 1 of an organic halogen compound decomposing apparatus to which the method for decomposing a halogen-based organic compound of the first invention of the present application is applied will be described with reference to FIG.

As shown in FIG. 1, the apparatus for decomposing organic halogen compounds according to the present embodiment employs an ultraviolet decomposing method which is expected to be most efficient in decomposing halogen-containing organic compounds. And an ultraviolet lamp 3. In addition, the decomposition tank 1 is filled with an appropriate amount of a reaction liquid (halogen-based organic compound) 1a in a liquid phase using alcohol as a solvent.

500 cc of an isopropyl alcohol solution containing 15 cc of CFC-11 as a halogenated organic compound 1a was placed in a decomposition tank 1 having an internal volume of 1000 cc, and CFC-11 was decomposed by irradiating with an ultraviolet lamp 3 for 10 minutes. Before and after decomposition, i.e., measuring the Freon concentration in the liquid before and after the irradiation of ultraviolet rays with a gas chromatograph,
The decomposition rate was calculated by the following formula.

Decomposition rate = 100 * (concentration before test-concentration after test) / (concentration before test) The obtained decomposition rate was 100%. Next, 100 cc of 15N caustic soda solution was added to precipitate the salt,
This was filtered with a filter. Add CFC-1 to this filtrate again.
15 cc of 1 and 60 cc of isopropyl alcohol were added and irradiated with ultraviolet rays. Similarly, as a result of measuring the decomposition rate, the decomposition rate was 100%. Again, alkali was added and the salt was separated. As a result of repeating this test, the decomposition rate was 100% by 20 times. The results are shown in FIG.

Next, the configuration of the second embodiment according to the second invention of the present application will be described with reference to FIG. FIG. 3 shows a schematic diagram of a halogen-based organic compound decomposing device in which the decomposition tank 1 and the alkali treatment tank 7 are provided separately. The organohalogen compound decomposing apparatus of the present embodiment is provided above the decomposing tank 1, a first process portion constituted by an ultraviolet lamp 3 provided in the decomposing tank 1, an alkali treating tank 7 and above the alkali treating tank 7. And a second process portion constituted by the liquid storage tank 9 that is provided.

Further, a liquid feed pump 5 for bidirectionally feeding the liquid to be decomposed is provided between the alkali treatment tank 7 and the decomposition tank 1, and the decomposition tank 1 is provided with a reaction liquid (halogen system). Organic compound) 1a, caustic soda solution 9a in storage tank 9
Are put in proper amounts. Further, a valve B is provided between the alkali treatment tank 7 and the liquid storage tank 9 to precisely control the injection amount of the caustic soda aqueous solution 9a to be injected from the liquid storage tank 9 into the alkali treatment tank 7. it can. Similarly, a valve B is also provided in the lower part of the alkali treatment tank 7, so that the salt deposited in the tank can be appropriately discharged to the outside of the tank.

500 cc of an isopropyl alcohol solution containing 15 cc of CFC-11 as a halogen-based organic compound 1a was put in a decomposition tank 1 having an internal volume of 1000 cc, and the CFC-1 was irradiated with ultraviolet rays from a UV lamp 3 for 10 minutes.
Disassemble 1. In the same manner as in Example 1, the fluorocarbon concentration in the liquid before and after the decomposition was measured by a gas chromatograph to obtain the decomposition rate. The obtained decomposition rate was 100%.

Next, the liquid to be decomposed after irradiation is transferred to the alkaline treatment tank 7 by the liquid feed pump 5, 100 CC of 15N caustic soda aqueous solution 9a is added to precipitate the formed salt 7b,
Solid-liquid separation was carried out by natural sedimentation, and it was removed outside the tank by a drain.

The liquid from which the drain has been removed is decomposed into the decomposition tank 1 again.
Then, 15 cc of CFC-11 and 60 cc of isopropyl alcohol were added and UV irradiation was performed. Similarly, the result of measuring the decomposition rate was 100%. Again, alkali was added to separate the salt 7b. As a result of repeating this test up to 20 times, the decomposition rate always showed 100%. The results are also shown in FIG.

Next, the third to tenth embodiments will be described. In Examples 3, to 10, the decomposition rate was measured by performing a decomposition test by the same operation using the same apparatus as in Example 2 except that the halogen-based organic compound to be treated was changed.
Table 1 shows the decomposition rates at the first and twentieth times. As is clear from Table 1, the decomposition rate of all the target substances was 90% or more even at the 20th time.

Next, Comparative Example 1 for comparison with Example 2
Will be described. In Comparative Example 1, the same apparatus as in Example 2 was used to perform a decomposition test on CFC-11 by the same operation to measure the decomposition rate. However, an isopropyl alcohol solution in which 5% of sodium had been previously substituted was used as a solvent.

The first-time decomposition rate in such an environment where alkali was present was 90%. Precipitated salt 7b
Was separated, CFC-11 and isopropyl alcohol were added, and UV irradiation was performed. As a result of the same measurement, the decomposition rate was 85%. As a result of repeating this test, the decomposition rate rapidly decreased to 50% at the 20th time, and the liquid was also colored. The change in the decomposition rate is also shown in FIG.

Further, Comparative Example 2 for comparison with Example 2 will be described. In Comparative Example 2, the same apparatus as in Example 2 was used to perform a decomposition test on CFC-11 by the same operation to measure the decomposition rate. However, an isopropyl alcohol solution to which a sodium aqueous solution was added in advance was used as a solvent.

The first decomposition rate in such an environment in which alkali was present was 95%. Precipitated salt 7b
Was separated, CFC-11 and isopropyl alcohol were added, and UV irradiation was performed. As a result of the same measurement, the decomposition rate was 90%. As a result of repeating this test, the decomposition rate decreased sharply to 70% at the 20th time, and the liquid was also lightly colored. The change in the decomposition rate is also shown in FIG.

In the above embodiment, the chlorofluorocarbon (CFC-1) is used.
1), the case of applying to trichlorethylene and PCB has been described as an example, but the present invention is not limited to this, and can be applied to any halogen-based organic compound.

Table 1 Examples Target substances Decomposition rate (%) 1st 20th 2 CFC-11 100 100 3 CFC-13 100 100 4 CFC-113 100 100 5 CFC-21 100 100 6 trichloroethylene 100 100 100 7 tetrachloroethylene 100 100 8 Monochlorobiphenyl 100 95 9 Trichlorobiphenyl 100 95 10 Pentachlorobiphenyl 100 90

[0035]

As described above, according to the present invention, the first step of irradiating the halogen-based organic compound with ultraviolet rays and the second step of treating with the alkali are separated.
The effects of significantly improving the decomposition efficiency and enabling the solvent to be recycled can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example to which a method for decomposing a halogen-based organic compound according to the present invention is applied.

FIG. 2 is a table showing the effects of the embodiment shown in FIG.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment according to the present invention.

[Explanation of symbols]

 1 Decomposition tank 1a Reaction liquid (halogen organic compound) 3 Ultraviolet lamp 5 Liquid feed pump 7 Alkali treatment tank 7b Formed salt 9 Storage tank 9a Caustic soda solution B valve

Claims (2)

[Claims] 1. A first step of irradiating a halogen-based organic compound in a liquid phase state with ultraviolet rays in an environment in which almost no alkali exists, and a second step of treating and removing a product produced by this irradiation with an alkali. And a step of decomposing a halogen-based organic compound. 2. A first step of irradiating a halogen-based organic compound in a liquid phase state with ultraviolet rays, and a salt produced by adding a necessary and sufficient amount of alkali to the product produced by this irradiation to produce the salt. And a second step of removing
The method for decomposing a halogen-based organic compound, which comprises performing the first step again in an environment in which the product and alkali hardly exist after the step.