JPH0679653B2 - Method for decomposing halogenated hydrocarbon and halogenated hydrocarbon decomposing agent used in the method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for decomposing halogenated hydrocarbons such as chlorinated hydrocarbons and fluorine-containing chlorinated hydrocarbons, and a halogenated hydrocarbon decomposing agent used in the method. It is about.

[Conventional technology]

As is well known, chlorinated hydrocarbons such as 1.1.1-trichloroethane, trichloroethylene, tetrachloroethylene are
It is inexpensive, nonflammable, and dissolves oils, tar, rubber, etc. well, and is widely used as a cleaning agent for fibers, machinery, films, electronic parts, and the like.

Chlorinated hydrocarbons have an acceptable concentration determined from their toxicity,
Countermeasures are regulated from the viewpoint of prevention of water pollution and groundwater pollution, but countermeasures against air pollution have not yet been regulated as a future problem. However, 1.1.1-trichloroethane, which is said to have the lowest toxicity among chlorinated hydrocarbons, became a problem with the decision to abolish specific CFCs such as CFC 113 in 2000 from the perspective of ozone layer depletion, and especially It is a big problem in the manufacturing industry where it is used as a cleaning agent, but no countermeasure has yet been taken.

A member of the inventors of the present invention conducts research in view of such a situation, and is capable of efficiently recovering halogenated hydrocarbons such as chlorinated hydrocarbons and fluorine-containing chlorinated hydrocarbons 1.3-dimethyl-2-imidazolidinone or Invented “Halogenated hydrocarbon recovery absorbent” containing N-methyl-2-pyrrolidone as an active ingredient and filed on May 1, 1991 (Japanese Patent Application No. 1-113300).
No.)

[Problems to be Solved by the Invention]

The above-mentioned prior invention is extremely suitable for reducing the concentration of halogenated hydrocarbons having a high concentration of about tens of thousands ppm in the air to a few hundreds of ppm, but it is extremely suitable for reducing the concentration of several hundreds of them in the air. pp
In order to further reduce the concentration of halogenated hydrocarbons having a low concentration of about m to about several tens of ppm, it is necessary to lower the temperature to -50 to -70 ° C or to absorb under pressure.

In order to reduce the concentration of low-concentration halogenated hydrocarbons of several hundred ppm to several tens of ppm in air to several ppm, adsorption by activated carbon is generally used. However, in this case, an absorption device having a large capacity is required, and adsorption regeneration is troublesome. Further, if steam desorption is performed, wastewater treatment is required, and measures for diffusion of adsorbed gas are also required when drying activated carbon.

In view of the above-mentioned current situation, the inventors of the present invention have found that several hundred pp
Low concentration halogenated hydrocarbon of m to several tens of ppm, specifically, halogen reduced to about several hundreds ppm to several tens of ppm by treating with the absorbent according to the above-mentioned prior invention. We have been conducting research to find a means that can efficiently treat dehydrocarbons to low concentrations of several tens to several ppm, but in the process of using 1.3-dimethyl-2-imidazolidinone as a solvent. Have obtained a remarkable new finding that halogenated hydrocarbons can be decomposed very efficiently by caustic alkali.

The present invention is based on the above-mentioned new knowledge, and a high concentration to a low concentration of halogenated hydrocarbons, especially about 10
It is a technical object to provide a technical means capable of efficiently and economically treating halogenated hydrocarbons of about 00 to 500 ppm down to 30 ppm or less.

[Means for Solving the Problems]

That is, the present invention provides the following method for decomposing a halogenated hydrocarbon and a halogenated hydrocarbon decomposing agent used in the method.

1.1.3-Dimethyl-2-imidazolidinone (hereinafter "DMI")
Said) and a caustic alkali mixed solution.

2. The halogenated hydrocarbon decomposing agent according to 1 above, to which water is added.

3. A method for decomposing a halogenated hydrocarbon, which comprises contacting the halogenated hydrocarbon with the halogenated hydrocarbon decomposing agent according to 1 or 2 above.

4. The method for decomposing a halogenated hydrocarbon according to the above 3, wherein the halogenated hydrocarbon and the halogenated hydrocarbon decomposing agent according to the above 1 or 2 are contacted at a temperature of 50 ° C to 150 ° C.

5. The method for decomposing a halogenated hydrocarbon according to the above 3 or 4, wherein the halogenated hydrocarbon is brought into contact with the halogenated hydrocarbon decomposing agent according to 1 or 2 in the presence of an alkali-resistant surfactant. .

First, the halogenated hydrocarbon decomposing agent according to the present invention will be described.

DMI has a boiling point of 225 ° C, is an aprotic polar solvent with almost no toxicity, and has excellent caustic resistance.

As the caustic alkali, caustic soda, caustic potash, calcium hydroxide and the like can be used, but caustic soda is preferable in consideration of economic efficiency, and caustic potash is preferable in consideration of decomposition efficiency.

The usage ratio of DMI and caustic can be freely selected.
It can be used in the state where the caustic alkali is completely dissolved in MI, or in the state where an excessive amount of caustic alkali is present in DMI in an undissolved state.

Further, it is also possible to put the container in a container filled with an excessive amount of caustic alkali, and while heating the container, make DMI flow down from the upper part and introduce halogenated hydrocarbon-containing air from the bottom part to cause contact and decomposition. .

When water is added, it will be about 3 relative to the DMI in which it is added.
It should be kept below 0% by volume, and the addition of more water will destroy the action of DMI as a decomposition solvent. A practically desirable ratio is 10% of DMI which is blended.
~ 20% by volume.

The decomposition ability of the halogenated hydrocarbon decomposing agent according to the present invention is extremely excellent as can be confirmed by the following examples.

Experimental example 1 (chlorinated hydrocarbon resolution) 1.1.1-Trichloroethane 1gr, DMI 1 in a pressure resistant glass container
Add 00ml, caustic soda 2.4gr and water 10ml, 2 at 100 ℃
Heated and stirred for an hour. The pressure rises to 0.5 kg / cm ² and 2
After a lapse of time, the pressure drops to 0.2 kg / cm ² , and when the temperature is lowered to room temperature, the pressure is reduced. In the contents after heating and stirring, DMI and concentrated caustic soda solution are separated, and crystals are suspended in the DMI layer and also adhered to the vessel wall. The DMI layer was taken out, the crystals were collected and dissolved in water, and NaCl was quantified with silver nitrate to obtain 1.436 gr of NaCl. This value is
The value calculated as the value decomposed by the following formula (1) 1.
It is almost the same as 314gr.

CH ₃ CCl ₃ ＋ 4NaOH → 3NaCl ＋ CH ₃ COONa ＋ 2H ₂ O (1) Experimental Example 2 (decomposition of fluorine-containing chlorinated hydrocarbons) 1.1.1-Trichloroethane was changed to Freon 11 and caustic soda was changed to caustic potassium 3.2gr. When an experiment was performed in the same manner as in Experimental Example 1, the same process as in Experimental Example 1 was performed, and 1.
57 gr of KCl was obtained. This value is almost the same as the value 1.63gr calculated as the value decomposed by the following equation (2).

CCl ₃ F + 6KOH → 3KCl + KF + K ₂ CO ₃ + 3H ₂ O (2) Experimental example 3 (fluorine-containing chlorinated hydrocarbon resolution) 1.1.1-Trichloroethane in Freon 113 with caustic soda
An experiment was conducted in the same manner as in Experimental Example 1 except that the heating / stirring time was changed to 3.4 gr and 2.5 hours, and 0.91 gr of NaCl was obtained after the same procedure as in Experimental Example 1. This value is
The value calculated as being decomposed by the following formula (3) 0.
It is almost the same as 94gr.

CFCl ₂ CF ₂ Cl ＋ 8NaOH → 3NaCl ＋ 3NaF ＋ NaOOC－COONa ＋ 4H ₂ O
(3) When treating the halogenated hydrocarbon in the air using the halogenated hydrocarbon decomposing agent according to the present invention having excellent resolution as described above, the target air is treated according to a conventional method. Collect and pass through the decomposer to make contact.

In this case, the contact may be carried out in the temperature range of room temperature (about 20 ° C.) to near the boiling point of DMI, but as seen in the following experimental example, the decomposition efficiency can be improved by increasing the temperature. Considering decomposition efficiency, workability, equipment, etc., a practically preferable temperature range is about 50 ° to 150 ° C.

Experimental Example 4 A mixed solution of 100 ml of DMI and 10 gr of powdered caustic soda was added.
While heating to 90 ° C and stirring, 500ppm of 1.1.1-
When trichlorethane-containing air was passed through 200 l at a flow rate of 0.1 / min, the concentration of 1.1.1-trichloroethane in the exhaust gas increased from 0 ppm to 60 ppm, and the decomposition rate was 95.4%. However, when the above temperature is set to 25 ° C, the decomposition rate is
It was 74%.

Further, the halogenated hydrocarbon decomposing agent according to the present invention, as seen in the following experimental examples, can perform stable treatment without its resolution being extremely lowered during use.

Experimental Example 5 A mixed solution of 100 ml of DMI, 10 gr of powdered caustic soda and 15 ml of water was heated to 100 ° C. and 100 l of air containing 1000 ppm of CFC 11 was passed through the mixture while stirring, and 100 l of air was passed at a flow rate of 0.1 / min. Decomposition rate 94%, Decomposition rate 95% at the next 30l, Decomposition rate 93% at the end 30l, average decomposition rate is 94%, and the concentration of Freon 11 in exhaust gas drops to 60ppm on average. did.

Further, as shown in Example 8 below, when the halogenated hydrocarbon decomposing agent according to the present invention is used, an appropriate amount of an alkali-resistant surfactant, for example, a perfluorohydrocarbon-based surfactant is used together, It is possible to improve the decomposition efficiency, especially in a system in which water is added to DMI, specifically, DMI.
It is effective for the dispersion system of a concentrated aqueous solution of caustic alkali.

In the halogenated hydrocarbon decomposing agent according to the present invention, the caustic alkali in the compounding components can be recovered as an alkali chloride or an alkali fluoride as shown in the above formulas (1) to (3), and the DMI is Can be reused as is.

[Action]

The decomposition mechanism of the halogenated hydrocarbon in the present invention reacts according to the above formulas (1) to (3). DMI, which is a solvent of this reaction, is an aprotic polar solvent, and particularly halogen of the halogenated hydrocarbon causing a strong polarization between carbon, carbon high hydroxy anion degree of freedom in which polarized in + (OH ^-) is attack C1 ^- reaction started by so-called "Sn-type reaction" to expel, subsequently, sequentially hydrolyzed Decomposes by decomposition reaction.

The above decomposition reaction is made possible by using DMI having strong alkali resistance and large polarity as a reaction solvent.

〔Example〕

 Next, the present invention will be described in more detail by way of examples.

A Dräger detector tube (manufactured by Dräger, West Germany) was used to measure the concentration of exhaust gas in each example.

Example 1 In a pressure-resistant glass autoclave, 1.1.1-trichloroethane 1 gr, DMI 100 ml as a decomposing agent, powdery caustic soda 2.4.
Then, gr and 10 ml of water were added, the mixture was sealed with Teflon ^R packing, and heated and stirred at 100 ° C. for 2 hours.

The amount of caustic soda per 1 mol of 1.1.1-trichloroethane is 8 mol, which is twice the calculated amount according to the above formula (1).

The pressure increased to 0.5 kg / cm ^2, after 2 hours reduced to 0.2 kg / cm ^2, a reduced pressure and lowering the temperature to room temperature.

After the temperature dropped to room temperature, the autoclave was opened and the DMI layer was taken out. The DMI layer is transparent and the aqueous solution of concentrated caustic soda is separated at the bottom. The pH of this DMI layer was 8.

Crystals are attached to the vessel wall.The crystals are washed out with methanol, dissolved in water and neutralized with dilute nitric acid to produce N / 10-AgNO ₃
The salt was titrated to obtain 1.46 gr of salt. The value calculated from the above formula (1) is 1.314gr, which is almost the same.

It has been confirmed that the recovered DMI can be reused as it is as the next decomposition agent.

Example 2 In a pressure-resistant glass autoclave were placed Freon 111 gr, DMI 100 ml as a decomposing agent, caustic potash 3.2 gr and water 15 ml, sealed, and heated and stirred at 80 ° C. for 2 hours.

In addition, the amount of caustic potash per 1 mol of Freon 11 is as described in (2) above.
Calculated according to the formula, this corresponds to 7.8 mol, which is 1.3 times equivalent.

The pressure rises to 0.6 kg / cm ² and after 1.5 hours 0.2 kg / cm ²
When the temperature is lowered to room temperature, the pressure is reduced.

After the temperature dropped to room temperature, the autoclave was opened and the DMI layer was taken out. The crystals adhering to the vessel wall were washed out with methanol, dissolved in 100 ml of water, neutralized with dilute nitric acid, 1N silver nitrate solution was added to precipitate silver chloride and silver fluoride, and heated and stirred with hot water. To dissolve silver fluoride, the silver chloride was filtered off, dried and weighed. 2.93 gr was obtained as silver chloride. This value corresponds to 93.3% of the theoretical amount.

Example 3 A freon 113 1 gr, DMI 100 ml as a decomposer, powdered caustic soda 3.4 gr and water 15 ml were placed in a pressure-resistant glass autoclave.
The mixture was put in, sealed, and heated and stirred at 100 ° C. for 2.5 hours.

The amount of caustic soda per 1 mol of Freon 113 is 16 mol as calculated according to the above formula (3), which is a double equivalent.

The pressure rises to 0.5 kg / cm ² and after 2.5 hours 0.5 kg / cm ²
When the temperature drops to room temperature, the pressure is reduced when cooled to room temperature.

After allowing to cool, open the autoclave, take out the DMI layer, wash the crystals adhering to the vessel wall with 30 ml of methanol, and wash with water.
Add 100 ml to dilute, neutralize with dilute nitric acid, add 1N silver nitrate to precipitate silver chloride and silver fluoride, heat and stir at 100 ° C to dissolve silver fluoride, and filter silver chloride. To do. The silver chloride obtained was 2.24 gr, which is in close agreement with the calculated value (2.30 gr).

Example 4 In a three-necked flask, 100 ml of DMI, 10 gr of powdered caustic soda and 15 ml of water were placed in a three-necked flask, and air containing 500 ppm of 1.1.1-trichloroethane was added thereto while heating and stirring at 90 ° C. I let it pass. In the early exhaust gas
The concentration of 1.1.1-trichloroethane is about 10 ppm, and 200 l
The concentration after passing was 30 to 35 ppm. The decomposition rate corresponds to 96.5%.

Example 5 The three-necked flask containing the decomposing agent used in Example 3 was allowed to stand, and after waiting for the separation of the DMI layer, the DMI layer was taken out,
5 gr of caustic potash was added to this DMI, placed in another 3-necked flask as a decomposing agent, and while heating and stirring at 130 ° C., 200 l of air containing 500 ppm of 1.1.1-trichloroethane was passed at a flow rate of 0.1 / min. It was From the initial exhaust gas 100l
1.1.1-Trichloroethane not detected, subsequent exhaust gas 1
It can be estimated that the concentration of 1.1.1-trichloroethane is about 10 ppm or less with a slight reaction of 00l in the detector tube. Therefore,
It can be said that the decomposition rate is close to 100%.

Example 6 DMI 100 ml as a decomposer, powdered caustic soda 10 gr and water 10 ml were placed in a three-necked flask and heated and stirred at 90 ° C., and 1000 ppm of a mixed gas of CFC 11 and air (CFC 11 42 μl / 90 l of air was passed through at a flow rate of 0.1 / min. The decomposition rate through the initial 30l is 95%, the decomposition rate through the next 30l is 94%, the decomposition rate through the last 30l is 91%, and the average decomposition rate is 93.3%. there were. In this case, the concentration of Freon 11 has dropped to 70 ppm on average.

Example 7 In a three-necked flask, 100 ml of DMI and caustic potash were used as a decomposing agent.
Add 0 gr and 1000 pp while heating and stirring at 120 ℃
Mixed gas of Freon 113 of m and air (Freon 113 54 μl / 10
l air) 100 l was passed at a flow rate of 0.1 / min. In this case, the decomposition rate of Freon 113 was 96.3%. Continue to 500pp
Mixed gas of m Freon 113 and air (Freon 113 27 μl / 10
l air) 100 l was passed at a flow rate of 0.1 / min. The decomposition rate in this case was 93.6%.

Example 8 To a three-necked flask, 100 ml of DMI, 5 gr of powdered caustic soda and 10 ml of water were placed as a decomposing agent, and 0.2 gr of a perfluorohydrocarbon-based surfactant (Surflon S-141: trade name: Asahi Glass) was added. Then, while heating and stirring at 100 ° C., 300 l of air containing 1000 ppm of 1.1.1-trichloroethane was passed through at a flow rate of 0.2 l / min. 1 out of 100 liters of initial exhaust gas.
The concentration of 1.1-trichloroethane was 0 to 10 ppm, the next concentration in 100 l was 10 to 20 ppm, and the final concentration in 100 l was 20 to 30 ppm. The decomposition rate corresponds to 98%.

In this case, the dispersion state of DMI and concentrated caustic soda solution in the flask was extremely good.

〔The invention's effect〕

According to the present invention as described above, halogenated hydrocarbons can be efficiently decomposed, and especially about 1000 to 500 p
Since it can efficiently and almost completely decompose halogenated hydrocarbons in the order of pm, it is currently regarded as an occupational health and safety problem due to specific CFCs and absorption toxicity that cause ozone depletion. 1.1.1-By carrying out the present invention for trichloroethane, various problems can be solved at once.

Further, in the case of combining the above-mentioned prior invention and the present invention, since it becomes possible to absorb and recover a high-concentration to medium-concentration halogenated hydrocarbon, and to decompose a low-concentration halogenated hydrocarbon, It is economical.

Furthermore, since the DMI in the present invention can be reused, it is economical from this point as well.

Therefore, it can be said that the present invention has extremely high industrial applicability.

Claims (5)

[Claims] 1. A halogenated hydrocarbon decomposing agent comprising a mixed solution of 1.3-dimethyl-2-imidazolidinone and caustic alkali. 2. The halogenated hydrocarbon decomposing agent according to claim 1, wherein water is added. 3. A method for decomposing a halogenated hydrocarbon, which comprises bringing the halogenated hydrocarbon into contact with the halogenated hydrocarbon decomposing agent according to claim 1 or 2. 4. The halogenated hydrocarbon according to claim 3, wherein the halogenated hydrocarbon and the halogenated hydrocarbon decomposing agent according to claim 1 or 2 are contacted at a temperature of 50 ° C. to 150 ° C. Disassembly method. 5. The halogenated hydrocarbon according to claim 3 or 4, wherein the halogenated hydrocarbon and the halogenated hydrocarbon decomposing agent according to claim 1 or 2 are contacted in the presence of an alkali-resistant surfactant. Hydrocarbon decomposition method.