JP3442623B2 - Decomposition method of halogen-containing organic compounds - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for decomposing a halogen-containing organic compound into a harmless substance, and more particularly to decomposing and dehydrogenating a halogen-containing organic compound to decompose the halogen-containing organic compound. And a method for decomposing a halogen-containing organic compound.

[0002]

2. Description of the Related Art Halogen-containing organic compounds such as trichlene, polychlorobiphenyl (PCB) and freon have been used in large amounts for various purposes. For example, PC
Since B has excellent insulation and flame retardancy, it is used as an electric insulating oil, a heat medium, and a flame retardant, and CFCs are used as a refrigerant and a cleaning liquid material due to its chemical stability and a low boiling point. It has been widely used in various fields such as the chemical industry.

However, with regard to chlorine compounds such as trichlene and PCB, toxicity to human bodies and bioaccumulation are problems, and a law concerning use regulation has been enacted. Fluorine compounds such as CFCs have recently been clarified as problems in terms of global environmental destruction as seen in ozone layer destruction. Under such circumstances, a method for decomposing the halogen-containing organic compound to render it harmless is required, and various methods have been studied.

The treatment of halogen-containing organic compounds is roughly divided into two types: decomposition by incineration and decomposition by chemical treatment. In decomposition by incineration, the halogen-containing organic compounds are burned at a high temperature of 800 ° C. or higher and decomposed. In the decomposition by chemical treatment, however, a halogen atom is desorbed from the halogen-containing organic compound by utilizing a chemical reaction and decomposed.

[0005]

However, in the decomposition by incineration, there is a possibility that the halogen-containing organic compound is converted into a more toxic substance by the action of heat, and in order to prevent this, the incineration treatment temperature should be set to an appropriate temperature. Need to be adjusted. Further, since hydrogen halide gas is generated by incineration, it is necessary to treat incineration exhaust gas.

On the other hand, for the decomposition by chemical treatment, there are a method of using a reagent such as an alkali metal such as sodium and an alkali metal compound such as sodium methylate, and a method of advancing dehalogenation under reducing conditions. For dehalogenation under reducing conditions, hydrogen-donating substances such as hydrogen gas, alcohol, and industrial oil are used.

The above-mentioned method using a reagent such as an alkali metal has a problem in terms of safety since the reagent is difficult to handle. Also, in dehalogenation under reducing conditions,
When a gas substance such as hydrogen is used as a hydrogen donor, the reaction is carried out under a very high pressure, and therefore a special device is required for safe treatment operation. On the other hand, in the case of liquid phase decomposition in which a liquid hydrogen donor is used for dehalogenation in a liquid phase, the reaction conditions are relatively mild, so that safe treatment is possible and there are advantages such as a small amount of exhaust gas. In particular, when alcohol is used as the hydrogen donor, the decomposition treatment of the organohalogen compound can be performed under extremely mild conditions. In this case, it is general to use an alkaline agent mainly for treating the eliminated halogen. However, when alkali hydroxide is used, water is generated along with the treatment, the solubility of the halogen-containing organic compound in the solvent decreases, the dispersibility in the solvent decreases, and the decomposition reaction becomes difficult to proceed. Also, will be changed into another substance alcohol which is a solvent that causes a condensation reaction by the action of an alkali hydroxide and heat, it can not be used effectively as a hydrogen supply material.

[0008]

According to the present invention, a halogen-containing organic compound can be safely and efficiently produced without causing problems such as the production of harmful substances and the necessity of treating exhaust gas or by-products as described above. It is an object of the present invention to provide a method for decomposing a halogen-containing organic compound that can be decomposed and rendered harmless.

[0009]

The method for decomposing a halogen-containing organic compound of the present invention is a halogen-containing organic compound in which a halogen-containing organic compound is dehalogenated by hydrogenation by reacting the halogen-containing organic compound with a hydrogen donor and an alkaline agent in the presence of a metal catalyst. A method for decomposing a compound, which uses alcohol as the hydrogen donor and metal hydride as the alkali agent.

When the reaction is carried out according to the above method, the metal catalyst replaces the halogen of the halogen-containing organic compound with hydrogen using the hydrogen-donating substance as a hydrogen source, and the released halogen atom is neutralized with an alkaline agent to form a salt. Stabilize. When alcohol is used as the hydrogen donor, a metal hydride is used as the alkaline agent, and when hydrogen by photolysis of water is used as the hydrogen donor, the alkaline agent is arbitrarily selected and both are neutralized salts. Form. Therefore, the reaction products of these reactions become stable and harmless substances. In addition, the decomposition treatment can be efficiently performed without generating a substance that inhibits the decomposition reaction or a substance that is difficult to handle.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The halogen-containing organic compound to be treated by the decomposition method of the present invention is a compound having a structure in which a halogen atom is bonded to carbon by a covalent bond, and examples thereof include methyl chloride, methylene chloride, chloroform and tetrachloride. carbon,
Examples thereof include halogenated alkanes such as trichlene and freon, halogenated benzenes such as chlorobenzene, halogenated biphenyls such as PCB, and chlorodibenzodioxin. Such compounds can be treated either alone or in the form of a mixture and can be applied in a mixture with halogen-free substances such as mineral oil.

In the decomposition method of the present invention, the halogen-containing organic compound as described above is reacted with a hydrogen source and an alkaline agent in the presence of a metal catalyst to promote the dehalogenation hydrogenation reaction of the halogen-containing organic compound. The compound is decomposed (ie converted to a halogen-free material).

The metal catalyst is selected from one or more of palladium, platinum, rhodium, ruthenium, iridium, osmium, iron, cobalt, nickel, manganese, chromium, molybdenum, tungsten, copper, zinc, tin, lead or compounds thereof. Preferably. In the case of a metal compound, it is preferably an oxide or a halogen compound.

The catalysts exemplified by the above-mentioned metals and metal compounds have an action of extracting hydrogen from a compound having hydrogen, and extract hydrogen from alcohol, for example. On the other hand, the halogen-containing organic compound tends to release halogen atoms easily due to the action of the alkali agent, rapidly releases the halogen atoms under the action of the catalyst, and becomes in an active state itself. The halogen-containing organic compound in this active state is
It is combined with hydrogen extracted by the catalyst mainly on the surface of the catalyst. As a result, the halogen-containing organic compound completes the replacement of the halogen atom with the hydrogen atom, and becomes a compound having a smaller number of halogen atoms. The dehalogenation hydrogenation reaction proceeds as long as the halogen-containing organic compound has a halogen atom, and finally the halogen-containing organic compound is completely dehalogenated and hydrogenated to be a harmless substance.

The amount of the above metal catalyst is preferably 0.0005 to 1 times the weight of the halogen-containing organic compound to be decomposed. The catalyst may be supported on a carrier,
In this case, as the carrier, activated carbon, carbon black,
Carbon carriers such as graphite are particularly suitable, but carriers such as zeolite, diatomaceous earth, magnesia, alumina, silica-alumina, cordierite and the like can be used, and may be appropriately selected as needed. The catalyst loading rate is preferably in the range of 1 to 20%.

In the above reaction, when alcohols are used as the hydrogen donor, the condensation reaction of the alcohol proceeds and complicated treatment is required to maintain the reaction system. It may interfere with the disassembly of. In order to prevent such a situation, the following two modes are adopted in the present invention. 1) Alcohol is used as a hydrogen supply substance and metal hydride is used as an alkaline agent.

2) As the hydrogen supplying substance, hydrogen obtained by decomposing water by light energy is used without using alcohol.

The above two modes will be described below.

(Use of alcohol / metal hydride) Examples of the metal hydride used in the present invention include alkali metal hydrides such as lithium hydride and sodium hydride, alkaline earth metal hydrides such as calcium hydride, and hydrogen. Examples thereof include tetrahydroborate salts such as sodium borohydride and tetrahydroaluminate salts such as lithium aluminum hydride, and lithium hydride is most suitable because it is easy to handle and obtain. When the amount of metal hydride used increases, the decomposition efficiency of the halogen-containing organic compound improves. However, if a metal hydride is used more than necessary, practical problems such as an excessive viscosity of the reaction solution and a limit of durability of the apparatus occur. Considering these points, the amount of metal hydride is preferably 1 to 30 times the number of moles of halogen of the halogen-containing organic compound to be treated.

The alcohol used in the present invention includes:
Alcohols having a tendency to easily release hydrogen by the action of a metal catalyst are preferable. In addition, it is preferable that it is a liquid at room temperature from the viewpoint of handling. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, and the like, but 2-propanol or ethanol is most preferable because hydrogen is easily released. The above alcohols may be used alone or in combination of two or more. The above alcohols need not be pure, and may be used as a mixture with other substances. These alcohols preferably have a water content of 1% or less so as not to impair the reactivity of the metal hydride.

The metal hydride is preferably used after being pulverized into fine particles and mixed with alcohol.

By bringing the metal hydride and the halogen-containing organic compound into contact with each other in the presence of the metal catalyst and alcohol described above, the dehalogenation hydrogenation reaction of the halogen-containing organic compound proceeds. Heat the reaction system if necessary,
The reaction rate may be increased to increase the processing rate. The temperature for heating is preferably in the range of room temperature to 150 ° C. in consideration of the boiling point of the solvent and the denaturation due to heat.

As in the present invention, a catalyst generally used in a reaction system in which a metal catalyst is added to a liquid is often in the form of fine particles and is dispersed in the reaction system for reaction. However, when the catalyst is fixed using a fixing means such as a column, and the reaction solution in which the metal hydride, the alcohol and the halogen-containing organic compound are mixed is repeatedly and constituted so as to come into contact with the fixed catalyst, the reaction is The subsequent catalyst recovery operation can be simplified or omitted.

(Use of hydrogen by decomposing water) Water is decomposed into oxygen and hydrogen when irradiated with light in the presence of a catalyst such as titanium oxide or zirconium oxide. If the hydrogen thus obtained can be used in the decomposition reaction of the halogen-containing organic compound, it is not necessary to use the alcohol as a hydrogen supply source in the decomposition of the halogen-containing organic compound. Does not happen. However, since the halogen-containing organic compound has low solubility in water, it is preferable that the photolysis of water and the decomposition of the halogen-containing organic compound are performed in separate systems. As a mode in which this can be carried out, a mode in which a photodecomposition system of water and a decomposition system of a halogen-containing organic compound are joined via a hydrogen permeable film can be mentioned. That is, only hydrogen generated in the photolysis system moves from the photolysis system to the decomposition system of the halogen-containing organic compound through the hydrogen-permeable film and is used for the decomposition reaction of the halogen-containing organic compound.

Examples of the hydrogen permeable membrane used in the above-mentioned form include a polysulfone membrane and a Teflon membrane. When a photodecomposition catalyst such as titanium oxide is supported on one surface of the hydrogen-permeable film that is in contact with the photodecomposition system, the migration distance of hydrogen generated by photodecomposition is shortened and efficiency is improved.

FIG. 1 shows an example of the disassembling apparatus according to the above embodiment.

The decomposition apparatus 1 of FIG. 1 comprises a reaction tube 3, a water tank 5, a liquid tank to be treated 7, pumps 9 and 11, and a lamp 13.
The inside of the reaction tube 3 is separated into a photolysis tank 17 and an organic tank 19 by the hydrogen permeable membrane 15. Water is circulated by the pump 9 to the photolysis tank 17 of the reaction tube 3. A liquid to be treated containing a halogen-containing organic compound and an organic solvent such as hexane is supplied from the liquid to be treated tank 7 to the organic tank 19 by a pump 11. Further, a metal catalyst for decomposing the alkaline agent and the halogen-containing organic compound is also supplied.

The wall portion 21 of the reaction tube 3 is made of titanium oxide, and transmits irradiation light such as ultraviolet light and sunlight radiated from the lamp 13 provided adjacent to the wall portion 21, and the wall portion 2
1, the photolysis of water in the photolysis tank 17 proceeds. Hydrogen generated by photolysis moves to the organic tank 19 through the hydrogen permeable film 15. When the irradiation light used for photolysis is sunlight, the lamp 13 can be omitted.

In this apparatus, the oxygen permeable membrane 15 is attached so as to be inclined, and the inside of the system of the photolysis tank 17 is narrower toward the upper side so that the generated hydrogen is easily transferred to the organic tank 19. The hydrogen permeable film 15 is made of Teflon, and titanium oxide is carried on the surface on the photolysis tank 17 side.
Even on the surface of 5, water is decomposed by the irradiation light transmitted through the wall portion 21. The decomposition reaction of the halogen-containing organic compound dissolved in the organic solvent proceeds on the metal catalyst in the organic tank 19 by using the hydrogen and the alkaline agent transferred to the organic tank 19. The dehalogenated halogen atom combines with the alkaline agent in the system to form a salt. Since salt is deposited in the organic tank 19 with the passage of time, the liquid to be treated in the organic tank 19 may be appropriately circulated.

In the above-mentioned apparatus 1, since a slight amount of heat is generated by light energy, it is not necessary to heat the organic tank 19 to raise the temperature, but when the decomposition reaction of the halogen-containing organic compound is promoted, it is 60 It does not matter if it is heated to about ℃. The solvent for dissolving the halogen-containing organic compound is not particularly limited as long as it is an aprotic solvent, but a hydrocarbon solvent that easily dissolves the halogen-containing organic compound is preferable, and hexane or the like that is easy to handle is most suitable.

As the alkaline agent to be supplied to the organic tank 19, potassium hydroxide has the highest reactivity, but there is no particular limitation as long as it can trap the desorbed halogen, and alkali metal hydroxide, alkaline earth metal hydroxide are available. Etc. can be used appropriately. The amount of the alkaline agent is preferably 10 times or more the molar amount of the halogen-containing organic compound. Further, the catalyst used here is preferably one having hydrogen transfer ability on the catalyst, a carbon-halogen bond breaking effect is high, and a catalyst which is easily dehydrohalogenated, specifically, palladium or rhodium is preferable, the such a catalyst active carbon, alumina, titania, to use by supporting the zirconia desirable. This supported catalyst preferably contains a small amount of water. Therefore, the supported catalyst is immersed in water in which an alkaline agent is dissolved and supplied to the organic tank 19. The halogen desorbed from the halogen-containing organic compound on the surface of the supported catalyst is absorbed and neutralized by the alkaline aqueous solution contained in the supported catalyst. The reaction time in the organic tank 19 may be several hours to several tens hours depending on the intensity of light and the concentration of the halogen-containing organic compound. Since the reactor is a closed type and no harmful substances are generated, it is a very safe and simple treatment method. The flow rate when the liquid to be treated is refluxed is not particularly limited.

[0034]

The present invention will be further described below with reference to examples.

Example 1 As a pretreatment, 0.8 g of lithium hydride and 0.2 g of palladium-supporting activated carbon (supporting rate 10% by weight) were dissolved in 100 mL of 2-propanol to prepare a temperature adjusting device and a stirring device. It was poured into a glass reaction container equipped with. After replacing the air in the reaction vessel with nitrogen, PCB (48% by weight of trichloride, 28% of tetrachloride)
%, Dichloride 16%, other 8%) 2.0
g was added to the reaction vessel. The reaction vessel was sealed, and the prepared solution was heated at 50 ° C. with stirring.

Heating time is 10 minutes, 20 minutes, 30 minutes and 1
Each time was set, and in each case, the solid content containing the catalyst was removed from the preparation liquid by filtration after heating was completed, and the PCB concentration of the preparation liquid was measured using a gas chromatograph.
The results are shown in Table 1.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that 4.0 g of sodium hydroxide was used instead of lithium hydride. The results are shown in Table 1.

Example 2 A reaction was carried out in the same manner as in Example 1 except that 0.2 g of platinum-supporting activated carbon (supporting rate 10% by weight) was used instead of palladium-supporting activated carbon. The results are shown in Table 1.

(Comparative Example 2) A reaction was carried out in the same manner as in Example 2 except that 4.0 g of sodium hydroxide was used instead of lithium hydride. The results are shown in Table 1.

(Example 3) 0.2 g of rhodium-supporting activated carbon (supporting rate 10% by weight) instead of palladium-supporting activated carbon
The reaction was performed in the same manner as in Example 1 except that was used. The results are shown in Table 1.

Comparative Example 3 A reaction was carried out in the same manner as in Example 3 except that 4.0 g of sodium hydroxide was used instead of lithium hydride. The results are shown in Table 1.

Example 4 A reaction was carried out in the same manner as in Example 1 except that 100 mL of ethanol was used instead of 2-propanol. The results are shown in Table 1.

(Comparative Example 4) A reaction was carried out in the same manner as in Example 4 except that 4.0 g of sodium hydroxide was used instead of lithium hydride. The results are shown in Table 1.

Example 5 A reaction was performed in the same manner as in Example 1 except that 2.0 g of trichlorobenzene was used instead of PCB. The results are shown in Table 2.

Comparative Example 5 A reaction was carried out in the same manner as in Example 5 except that 4.0 g of sodium hydroxide was used instead of lithium hydride. The results are shown in Table 2.

Examples 6 to 9 In place of lithium hydride, in Example 6 2.4 g of sodium hydride, Example 7
The reaction was performed in the same manner as in Example 1 except that 4.2 g of calcium hydride was used, 3.8 g of sodium borohydride was used in Example 8, and 3.8 g of lithium aluminum hydride was used in Example 9. The results are shown in Table 3.

[0047]

[Table 1] −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−                                 PCB concentration (ppm)               Before processing 10 minutes 20 minutes 30 minutes 1 hour −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 25000 90 1.1 0.027 <0.0005 Comparative Example 1 25000 1500 90 3.2 0.240 Example 2 25000 250 5.2 0.095 0.0014 Comparative Example 2 25000 6500 920 70 0.0085 Example 3 25000 430 10 0.310 0.0027 Comparative Example 3 25000 9800 1300 220 32 Example 4 25000 130 3.9 0.078 <0.0005 Comparative Example 4 25000 3800 240 0.019 1.2 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−                                                       Lower limit of quantification: 0.5ppb

[Table 2] −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−                           Trichlorobenzene concentration (ppm)               Before processing 10 minutes 20 minutes 30 minutes 1 hour −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 5 25000 1.7 0.044 <0.005 <0.005 Comparative Example 5 25000 160 2.9 320 0.850 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−                                                       Lower limit of quantification: 5ppb

Table 3 ------------------ PCB concentration (ppm) 10 minutes before treatment 20 Minutes 30 minutes 1 hour ----------------------------------------- Example 1 25000 90 1.1 0.027 <0.0005 Example 6 25000 140 2.8 0.100 0.0017 Example 7 25000 260 8.6 0.420 0.0069 Example 8 25000 110 1.2 0.015 0.0008 Example 9 25000 200 3.0 0.034 0.0015 −−−−−−−−−−−−−−−−−−− −−−−−−−−−−−−−−−−− Lower limit of quantification: 0.5 ppb (Example 10) A Teflon membrane (hydrogen permeability: 0.45 g) configured as shown in FIG. / 100 in ² /
24hr / (atm / mil) (40 ℃), 0.85g / 100in
^{2 / 24hr / (atm / mil} ) (60 ℃)) using the apparatus 1 provided with, was poured into the treatment tank 7 by dissolving PCB-containing oil in hexane as solvent (2% PCB concentration), Pd /
Water having a concentration of 20% potassium hydroxide was immersed in 5 g of C catalyst and added to the organic tank 19, and the PCB solution was supplied from the liquid tank 7 to be processed to the organic tank 19. Water was circulated from the water tank 5 to the photolysis tank 17.

The photolysis tank 17 was irradiated with the energy of the sunlight wavelength from the lamp 13, and after 10 hours, the residual PCB in the solvent in the organic tank 19 was measured by GC / MS.
It was below the detection limit (10 ppb). Therefore, this PC
B was completely decomposed.

(Comparative Example 6) PCB (KC-300) 100 ppm in three glass flasks with an internal volume of 300 mL.
, C-type heavy oil containing a carbon-based catalyst and sodium hydroxide was added, and the mixture was stirred in a nitrogen atmosphere at atmospheric pressure and stirred at 300 ° C. or higher for 6 hours with a mantle heater. PCB was detected as a result of filtering after 6 hours and analyzing the filtrate by GC / MS. From the detected value, the decomposition rate of PCB is 99.9%,
The PCB remained slightly.

(Embodiment 11) A polysulfone membrane is used as the hydrogen permeable membrane 15 of the device 1, and in the liquid tank 7 to be treated in the same manner as in Embodiment 10, hexane is used as a solvent and PCB has a concentration of 1.
The solution dissolved in% was added. A solution obtained by immersing an aqueous solution of 20% potassium hydroxide in 5 g of Pd / C catalyst was added to the organic tank 19, and the PCB solution was supplied to the organic tank 19 from the liquid tank 7 to be treated. The water is circulated to the photolysis tank 17, and the lamp 13 irradiates the light energy of the wavelength of the sunlight,
After the time, the residual PCB of the solvent was measured by GC / MS, and the result was below the lower limit of detection. Therefore, this PCB was completely decomposed.

(Embodiment 12) The wall portion 21 is made of glass, and the hydrogen permeable film 15 having titanium oxide supported on the surface of the polysulfone film is used to fabricate a device having a structure as shown in FIG. An aqueous trichlene solution (concentration: 120 ppm) was charged into the treatment liquid tank 7 and supplied to the organic tank 19. To the organic tank 19, an aqueous solution having a concentration of 20% calcium hydroxide immersed in 5 g of Pd / C catalyst was added. Photolysis tank 1
The water was circulated in No. 7 and the lamp 13 was irradiated with light energy having a wavelength of sunlight, and the concentration of trichlene in the solvent after 12 hours was analyzed by GC-ECD. Therefore, trichlene was completely decomposed.

As will be understood from the above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention.

[0053]

As described above, according to the present invention, the halogen-containing organic compound can be decomposed efficiently, so that the treatment of the unnecessary halogen-containing organic compound can be simplified.
It is also excellent in that the treatment after the reaction is easy. Therefore, its value in industry and environmental protection is great.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a decomposition apparatus for decomposing a halogen-containing organic compound according to the present invention.

[Explanation of symbols]

1 Decomposing device 3 reaction tubes 5 water tank 7 liquid tank 9,11 pump 13 lamps 15 Hydrogen-permeable membrane 17 Photolysis tank 19 organic tank 21 wall

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B01J 35/02 B01J 35/02 J C02F 1/30 C02F 1/30 1/58 1/58 A (56) References 52-36650 (JP, A) JP 62-74452 (JP, A) JP 10-249313 (JP, A) JP 60-218330 (JP, A) JP 4-26632 (JP, A) JP-A-4-261675 (JP, A) JP-A-8-266888 (JP, A) JP-A-9-122479 (JP, A) JP-A-7-51401 (JP, A) JP-A-60 -118289 (JP, A) JP-A-57-205301 (JP, A) JP-A-49-41344 (JP, A) JP-A-54-59233 (JP, A) (58) Fields investigated (Int.Cl) . ⁷ , DB name) C02F 1/70 A62D 3/00 C07B 35/06 C07B 61/00 B01J 23/40 B41J 35/02 C02F 1/30 C02F 1/58

Claims (2)

(57) [Claims] 1. A method for decomposing a halogen-containing organic compound by dehydrohalogenating a halogen-containing organic compound by reacting the halogen-containing organic compound with a hydrogen donor and an alkaline agent in the presence of a metal catalyst, wherein A method for decomposing a halogen-containing organic compound, which comprises using a metal hydride as the alkali agent as the hydrogen donor. 2. The metal hydride is an alkali metal hydrogen
Compounds, alkaline earth metal hydrides, tetrahydroboric acid
Selected from the group consisting of salts and tetrahydroaluminates
The decomposition method according to claim 1, further comprising: