JPH09249582A - Decomposition of halogen-containing organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for decomposing a halogen-containing organic compound by which the halogen-containing organic compound can efficiently and safely be decomposed and detoxified. SOLUTION: A halogen-containing organic compound is heated in the coexistence of a metal belonging to the platinum group or the iron family or a compound of the metal, an aliphatic hydrocarbon solvent and an alkaline substance and thereby dehalogenated. The halogen-containing organic compound is heated at 150-400 deg.C temperature in a pressurized atmosphere under 1-11atm pressure.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for decomposing a halogen-containing organic compound into harmless substances, and more particularly to a decomposition method for decomposing a halogen-containing organic compound by dehalogenating and hydrogenating the organic compound.

[0002]

2. Description of the Related Art Trichlorene, polychlorobiphenyl (P
Halogen-containing organic compounds such as CB) and chlorofluorocarbon have been used in large amounts for various purposes. For example, since PCB has excellent insulating properties and flame retardancy, it can be used as an electric insulating oil, a heat carrier, and a flame retardant, and CFCs can be used as a refrigerant or a cleaning liquid material due to its chemical stability and low boiling point. Parts industry,
Widely used in various fields such as chemical industry.

However, chlorine compounds such as trichlene and PCB have been shown to be toxic to the human body and have high bioaccumulation potential. Fluorine compounds such as CFCs have recently been found to have problems in terms of global environmental destruction as seen in ozone layer depletion. 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 risk 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. When a liquid hydrogen-donating substance such as alcohol or industrial oil is used, the liquid is mixed with a halogen-containing organic compound and heated in the liquid phase to cause dehalogenation / hydrogenation reaction, which results in liquid-phase decomposition.

The above-mentioned method using a reagent such as an alkali metal has a problem in safety since it is difficult to handle the reagent. Also, in dehalogenation under reducing conditions,
When using a gas substance such as hydrogen as a hydrogen donor,
Since the reaction is carried out under extremely high pressure, special equipment is required for safe processing operation. On the other hand, in the case of liquid phase decomposition in which a liquid hydrogen donor is used to dehalogenate in the liquid phase, the reaction conditions are relatively mild, so safe processing is possible and there are advantages such as less exhaust gas. However, there is a drawback that the treatment takes a long time because the reactivity of the hydrogen donor is low.

[0008]

The present invention includes a method for safely and efficiently decomposing and detoxifying a halogen-containing organic compound without causing problems such as the production of harmful decomposition products and the necessity of treating exhaust gas as described above. An object is to provide a method for decomposing a halogen organic compound.

The method for decomposing a halogen-containing organic compound according to the present invention is a method of decomposing a halogen-containing organic compound in the coexistence of a metal belonging to the platinum group or the iron group or a compound of the metal, an aliphatic hydrocarbon solvent and an alkaline substance. The halogen-containing organic compound is dehalogenated by heating.

In the above method, the halogen-containing organic compound is heated in a pressurized atmosphere of 1 to 11 atm. Further, the halogen-containing organic compound is heated to a temperature of 150 to 400 ° C.

When heating is performed according to the above method, the metal belonging to the platinum group or the iron group or the compound of the metal is
It acts as a catalyst to extract hydrogen from the aliphatic hydrocarbon solvent. Further, the catalyst abstracts the halogen atom of the halogen-containing organic compound and replaces it with hydrogen on the surface of the catalyst. The halogen atom extracted from the halogen-containing organic compound combines with hydrogen on the catalyst surface to form hydrogen halide, which is neutralized by the alkaline substance. .

[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 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 alone or in the form of a mixture, and can be applied to a mixture with a halogen-free substance such as mineral oil.

In the decomposition method of the present invention, the halogen-containing organic compound as described above is heated in the coexistence of a catalyst, a hydrocarbon solvent and an alkaline substance, whereby the dehalogenation reaction of the halogen-containing organic compound proceeds, The compound is decomposed (ie converted to a halogen-free material).

The catalyst is a metal belonging to the platinum group such as palladium, platinum, ruthenium, rhodium; iron, cobalt,
It is preferable to select from simple substances of metals belonging to the iron group such as nickel; and compounds of the metals. In the case of a metal compound, it is preferably a halide. Particularly, palladium and its compound are preferable.

The catalysts exemplified by the above-mentioned metals and metal compounds have a function of extracting hydrogen from a compound having hydrogen, and in the reaction system according to the present invention, hydrogen is extracted from a hydrocarbon solvent. The abstracted hydrogen is replaced with the halogen atom of the halogen-containing organic compound on the catalyst surface. As a result, the halogen-containing organic compound is dehalogenated and hydrogenated. The desorbed halogen atoms on the catalyst surface are desorbed from the catalyst as hydrogen halide and are neutralized by the alkaline substance.

The amount of the catalyst is preferably 0.01 to 5 times the weight of the halogen-containing organic compound to be decomposed.
The catalyst may be supported on a carrier. In this case, carbon carriers such as activated carbon, carbon black and graphite are particularly suitable as the carrier, but zeolites, diatomaceous earth, magnesia, alumina, cordierite, etc. Various carriers can be used, and may be appropriately selected as needed. The catalyst loading rate is preferably in the range of 0.5 to 10%.

Therefore, the hydrocarbon solvent is a source of hydrogen, and the catalyst is a compound which easily extracts hydrogen. For such a role, it is preferable to use an aliphatic hydrocarbon, for example, a straight chain hydrocarbon such as hexane, decane and tridecane, a hydrocarbon having a branched chain such as isooctane and dimethylhexadecane, cyclohexane and cyclododecane. Aromatic hydrocarbons are not suitable as the hydrocarbon solvent of the present invention because the extraction of hydrogen by a catalyst is not easy due to the electron resonance structure. The hydrocarbon solvent may be used alone or in combination of two or more kinds. You may mix and use with hydrocarbon solvents other than an aliphatic hydrocarbon. In this case, the proportion of aliphatic hydrocarbon is preferably 50% by weight or more. From the viewpoint of economy and availability, heavy oil, light oil, kerosene,
It can be said that mineral oil such as benzine is particularly suitable for practical use. The amount of the hydrocarbon solvent used is preferably 5 to 1000 times the weight of the halogen-containing organic compound. The hydrocarbon solvent is a liquid at room temperature and atmospheric pressure, but it is preferable that it can exist as a liquid phase or a part of the liquid phase even under reaction conditions. When the boiling point of the hydrocarbon solvent is lower than the reaction temperature, For example, the hydrocarbon can be made to exist in the liquid phase by raising the boiling point of the hydrocarbon by sealing or pressurizing the reaction vessel or by mixing it with a high-boiling medium. The high boiling point medium is not particularly limited as long as it does not inhibit the action of the catalyst to extract hydrogen from the hydrocarbon solvent, and aromatic hydrocarbon or the like may be applied to the high boiling point medium.

As the alkaline substance used in the present invention, a hydroxide of an alkali metal or an alkaline earth metal is preferable, and among them, sodium hydroxide or potassium hydroxide is suitable from the viewpoint of economy. When the amount of the alkaline substance used is increased, the decomposition efficiency of the halogen-containing organic compound is improved, and it is preferable to use the alkaline substance in an amount equal to or more than twice the number of moles of halogen of the halogen-containing organic compound to be treated. However, if the amount exceeds 30 times the molar equivalent, practical problems such as excessive viscosity of the reaction solution and the limit of resistance of the apparatus occur. Alkaline substances do not dissolve in hydrocarbons,
It is pulverized into fine particles and added to the reaction system.

In the reaction system of the present invention, the alkaline substance not only neutralizes the hydrogen halide but also promotes the action of weakening the covalent bond of the halogen atom in the halogen-containing compound and the elimination of the halogen atom from the catalyst surface. Like action,
It is considered to play an auxiliary role in the progress of the reaction.

By heating the halogen-containing organic compound together with the catalyst, hydrocarbon solvent and alkali described above, dehalogenation of the halogen-containing organic compound proceeds. The heating temperature is preferably in the range of 150 to 400 ° C.
If the temperature is lower than 150 ° C., the reaction does not proceed, and if it exceeds 400 ° C., an unintended reaction such as a polymerization reaction of a hydrocarbon or a halogen-containing organic compound proceeds.

When the reaction vessel is closed and heated, the pressure inside the reaction vessel increases due to the vaporization pressure of the hydrocarbon and the halogen-containing organic compound. The decomposition reaction of the halogen-containing organic compound according to the present invention can be carried out either at normal pressure or under pressure, but if it is carried out under pressure, the efficiency of the decomposition reaction is dramatically improved. Therefore, it is preferable to carry out the decomposition reaction under pressure so that the atmospheric pressure is about 1 to 11 atm (0 to 10 atm in gauge pressure), preferably 2 to 8 atm (1 to 7 atm in gauge pressure). If the pressure of the reaction system exceeds 11 atm, the hydrocarbon is likely to be denatured, that is, the condensation reaction of the aliphatic hydrocarbon may proceed to be converted into the aromatic hydrocarbon. Aromatic hydrocarbons are also difficult to use as fuel oil and the like, which is not preferable in consideration of treatment of hydrocarbons after reaction and diversion to other purposes.

Carrying out the decomposition reaction in a closed container also has the advantage that there is no danger of releasing toxic substances outside the reaction system and the safety is high. Further, it is also excellent in that even a halogen-containing organic compound having a low boiling point can be efficiently decomposed without being vaporized outside the system.

The catalyst generally used in the reaction system in which the catalyst is added to the solvent as in the present invention is often a catalyst having a fine particle shape, and the catalyst is dispersed in the reaction system and reacted. However, when the catalyst is fixed by using a fixing means such as a column, and the reaction is carried out so that the hydrocarbon solvent mixed with the alkaline substance and the halogen-containing organic compound is repeatedly brought into contact with the fixed catalyst, the reaction of the catalyst after the reaction is The collection operation can be omitted.

[0025]

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

(Example 1) As a pretreatment, PCB (56% by weight of pentachloride, 21% by weight of tetrachloride and 21% by weight of tetrachloride)
2.0 g, palladium-supported activated carbon (support rate 10% by weight)
2.0 g and 15.0 g of potassium hydroxide 100 ml of heavy oil
The prepared solution mixed with was poured into a stainless steel reaction vessel equipped with a stirrer, nitrogen gas was blown into the prepared solution to expel dissolved oxygen, and the inside of the reaction vessel was replaced with nitrogen gas. Then, the reaction vessel was sealed by removing excess nitrogen gas so that the pressure inside the reaction vessel became atmospheric pressure.

After that, the reaction vessel was heated while stirring the preparation liquid with a stirrer to raise the temperature of the preparation liquid to 300 ° C., and this temperature was maintained for 2 hours. During this time, the pressure in the reaction vessel was 4.1 when the temperature of the preparation liquid reached 300 ° C.
It became atm, then gradually increased for 2 hours to 6.2 a
Reached tm.

After completion of heating, the reaction vessel was cooled to room temperature, the solid content containing the catalyst and potassium hydroxide was removed from the prepared solution by filtration and centrifugation, and the PCB concentration of the prepared solution was measured using a gas chromatograph. . The results are shown in Table 1.

Example 2 Using the same stainless steel reaction container except that the volume of the reaction container was larger than that of Example 1, the same pretreatment operation as in Example 1 was repeated to contain the preparation liquid. A reaction container was prepared.

The reaction vessel was heated in the same manner as in Example 1, and when the temperature reached 300 ° C., the pressure inside the reaction vessel was 2.0.
It became atm and then gradually increased for 2 hours to 2.7 a
Reached tm.

After the heating was completed, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1 to measure the PCB concentration of the preparation liquid. The results are shown in Table 1.

(Example 3) The same pretreatment operation as in Example 1 was repeated using the same stainless steel reaction container except that the volume of the reaction container was smaller than that of Example 1, and the preparation liquid was added. A reaction container was prepared.

The reaction vessel was heated as in Example 1, and when the temperature reached 300 ° C., the pressure inside the reaction vessel was 6.0.
became atm, then gradually increased for 2 hours to 9.8 a
Reached tm.

After the heating was completed, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1 to measure the PCB concentration of the preparation liquid. The results are shown in Table 1.

Example 4 The same pretreatment and heating operations as in Example 1 were carried out except that 0.2 g of palladium powder prepared from palladium chloride by a conventional method was used instead of the palladium-supported activated carbon.

After the end of heating, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1 to measure the PCB concentration of the preparation liquid. The results are shown in Table 1.

(Example 5) Palladium-supporting zeolite (supporting ratio: 10% by weight) was used in place of the palladium-supporting activated carbon.
The same pretreatment operation and heating operation as in Example 1 were performed except that 2.0 g was used.

After the heating, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1 to measure the PCB concentration of the preparation liquid. The results are shown in Table 1.

Example 6 The same pretreatment and heating operations as in Example 1 were carried out except that the amount of potassium hydroxide added was changed to 7.5 g.

After the heating, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1 to measure the PCB concentration of the preparation liquid. The results are shown in Table 1.

(Example 7) Using a stainless steel reaction vessel equipped with a stirrer and a reflux condenser, the same pretreatment operation as in Example 1 was repeated to prepare an open system reaction vessel containing the preparation liquid. . The reaction vessel was heated while cooling the reflux condenser so that the components of the preparation liquid did not leak outside the reaction vessel, and when the temperature reached 300 ° C, the temperature of 300 ° C was maintained for 2 hours. After the heating, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 1, and the PCB concentration of the preparation liquid was measured. The results are shown in Table 1.

(Embodiment 8) As a pretreatment, Freon (CF
C-11) 3.0 g, palladium-supported activated carbon (support rate 1
(0% by weight) 2.0 g and potassium hydroxide 24.2 g mixed in 100 ml of heavy oil was poured into a stainless reaction vessel equipped with a stirrer, and nitrogen was introduced at a gentle rate so that CFCs would not leak from the reaction vessel. Gas was blown into the prepared liquid to expel dissolved oxygen, and the inside of the reaction vessel was replaced with nitrogen gas. Then, the reaction vessel was sealed by removing excess nitrogen gas so that the pressure inside the reaction vessel became atmospheric pressure.

After this, the reaction vessel was heated while stirring the preparation liquid with a stirrer to raise the temperature of the preparation liquid to 275 ° C., and this temperature was maintained for 1 hour. During this period, the pressure in the reaction vessel is 5.0 when the temperature of the prepared solution reaches 275 ° C.
It became atm and then gradually increased for 1 hour to 8.3 a
Reached tm.

After completion of heating, the reaction vessel was cooled to room temperature, the solid content containing the catalyst and potassium hydroxide was removed from the prepared solution by filtration and centrifugation, and the freon concentration of the prepared solution was measured using a gas chromatograph. . The results are shown in Table 1.

(Example 9) Using a stainless reaction vessel equipped with a stirrer and a reflux condenser, the same pretreatment operation as in Example 8 was repeated to prepare an open type reaction vessel containing the preparation liquid. . The reaction vessel was heated while cooling the reflux condenser so that the components of the preparation liquid would not leak out of the reaction vessel, and when the temperature reached 275 ° C, the temperature of 275 ° C was maintained for 1 hour. After the heating was completed, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 8, and the freon concentration of the preparation liquid was measured. The results are shown in Table 1.

(Example 10) As a pretreatment, 2.0 g of 1-chlorohexane and palladium-supported activated carbon (supporting rate: 10) were used.
Wt%) 2.0 g and potassium hydroxide 9.2 g to heavy oil 1
The prepared solution mixed with 00 ml was poured into a stainless steel reaction vessel equipped with a stirrer, nitrogen gas was blown into the prepared solution to expel dissolved oxygen, and the inside of the reaction vessel was replaced with nitrogen gas. Then, the reaction vessel was sealed by removing excess nitrogen gas so that the pressure inside the reaction vessel became atmospheric pressure.

Then, the reaction vessel was heated while stirring the preparation liquid with a stirrer to raise the temperature of the preparation liquid to 300 ° C., and this temperature was maintained for 1 hour. During this time, the pressure in the reaction vessel was 2.0 when the temperature of the preparation liquid reached 300 ° C.
Atm, then gradually rises to 3.5 a for 1 hour
Reached tm.

After the heating is completed, the reaction vessel is cooled to room temperature, the solid content containing the catalyst and potassium hydroxide is removed from the preparation liquid by filtration and centrifugation, and the 1-chlorohexane concentration of the preparation liquid is measured by using a gas chromatograph. Was measured. The results are shown in Table 1.

Example 11 Using a stainless steel reaction vessel equipped with a stirrer and a reflux condenser, the same pretreatment operation as in Example 10 was repeated to prepare an open system reaction vessel containing the preparation liquid. .

The reaction vessel was heated while cooling the reflux condenser so that the components of the preparation liquid would not leak out of the reaction vessel, and when the temperature reached 300 ° C., the temperature of 300 ° C. was maintained for 1 hour. After the heating was completed, the preparation liquid was cooled and the solid content was removed in the same manner as in Example 10, and the 1-chlorohexane concentration of the preparation liquid was measured. The results are shown in Table 1.

[0051]

[Table 1] -------------------------------------- Halogen-containing compound Reaction temperature Pressure Halogen-containing compound concentration Heating Before heating (° C) (atm) (ppm) (ppm) −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Example 1 PCB 300 4.1-6.2 21000 0.047 Example 2 PCB 300 2.0-2.7 21000 0.22 Example 3 PCB 300 6.0-9.8 21000 0.044 Example 4 PCB 300 4.1-6.2 21000 0.62 Example 5 PCB 300 4.1-6.2 21000 0.13 Example 6 PCB 300 4.1-6.2 21000 0.19 Example 7 PCB 300 1.0 21000 3.9 Example 8 Freon 275 5.0-8.3 19600 0.43 Example 9 Freon 275 1.0 19600 95 Example 10 Chlorohexane 300 2.0-3.5 20600 0.20 Example 11 Chlorohexane 300 1.0 20600 55 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

In the above example, all three halogen-containing organic compounds decomposed efficiently. In this,
Examples 7, 9, and 11 use an open type reaction vessel,
The heating atmosphere is atmospheric pressure. Comparing the results of these examples and other examples, it is understood that the decomposition of the halogen-containing organic compound progresses when heated under pressure. Further, since the decomposition can be performed with high efficiency at a relatively low pressure of about 2 atm, the safety is much higher than that of the conventional method using hydrogen gas or the like. When the reaction vessel is closed, the internal pressure of the reaction vessel gradually increases during heating at a constant reaction temperature because the heavy oil used as a solvent is pyrolyzed to become a light hydrocarbon. it is conceivable that. From this, it is understood that the lightening of the heavy oil by the thermal decomposition and the decomposition of the halogen-containing organic compound can be performed at the same time.

Further, from Examples 1, 4 and 5, it is understood that supporting the catalyst on the activated carbon improves the decomposition efficiency as compared with the case of using another carrier or the case of no carrier. Further, from the comparison between Examples 1 and 6, it can be seen that the decomposition efficiency is improved when the amount of the alkaline substance is increased. That is, the alkaline substance contributes not only to the neutralization of hydrogen halide but also to the progress of the decomposition reaction.

[0054]

As described above, according to the present invention,
Since the decomposition of halogen-containing organic compounds is performed efficiently,
It is also excellent in that the treatment of the halogen-containing organic compound that has become unnecessary is easy and the treatment after the reaction is easy, and its value in industry and environmental protection is great.

Claims (3)

[Claims] 1. A halogen-containing organic compound is removed by heating the halogen-containing organic compound in the coexistence of a metal belonging to the platinum group or the iron group or a compound of the metal, an aliphatic hydrocarbon solvent, and an alkaline substance. A method for decomposing a halogen-containing organic compound, which comprises halogenating. 2. The halogen-containing organic compound is 1 to 11 atm.
The heating is performed in a pressurized atmosphere according to claim 1.
A method for decomposing the halogen-containing organic compound described. 3. The halogen-containing organic compound is 150 to 40.
The method for decomposing a halogen-containing organic compound according to claim 1 or 2, wherein the decomposition is performed at a temperature of 0 ° C.