JP2000334062A - Microwave-solvothermal treatment of harmful organic compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a continuous, safe, and energy-saving closed system for treatment of harmful organic chlorinated compounds operating under such milder conditions as low temperature and low pressure. SOLUTION: Harmful organic compounds and solutions containing these are mixed with an aqueous alkaline solution, continuously injected into a reactor, and irradiated with microwave to continuously decompose and detoxify the harmful compounds above its boiling point and under pressure. In the reacting portion of the reactor is provided a catalyst that absorbs microwave and decomposes the organic compounds. The catalysts are oxides of metals or their compound oxides, or composite materials made by coating the surface of porous materials with these oxides. The microwave is irradiated continuously or by pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of heating a harmful organic compound such as an organic halogen compound and a polycyclic aromatic compound by microwave irradiation and continuously heating the harmful organic compound at a temperature and pressure higher than the boiling point, that is, under solvothermal conditions. It relates to a method of decomposing and rendering harmless.

[0002]

2. Description of the Related Art Hazardous substances such as organic halogen compounds are not only highly toxic, but even in very small amounts, endocrine disruptors (environmental hormones), which greatly affect reproduction, are being developed as processing technologies. Pollution on a large scale has become a major social problem.

[0003] Recently, the decomposition of organic halogen compounds by the wet decomposition method, particularly the supercritical water decomposition method, has attracted attention and has been actively studied. In these methods, the temperature is between 400 and 50
The treatment is performed under the conditions of high temperature and high pressure of 0 ° C. and pressure of 100 to 300 atm. Yamazaki et al. Hydrothermally decompose organochlorine compounds such as PCB and TCE under low-temperature and low-pressure conditions of about 200 to 350 ° C. and about 100 atm [N. Yamasaki et al.
Env. Sci. Tech., 14 (5), 550 (1990)]. Subcritical and supercritical water are highly corrosive, and corrosive gases are generated from organic halogen compounds, and a reactor with good pressure resistance, heat resistance and corrosion resistance is required. In addition, although alkali is used as a dechlorinating agent, it becomes co-solvent in supercritical water, the solubility of ionic substances decreases, and salts such as sodium chloride are precipitated.

[0004] It is known that by irradiating a reaction tube filled with a catalyst such as silicon carbide or the like with microwaves to a predetermined temperature and continuously injecting an organic chlorine compound or the like, the organic chlorine compound is efficiently decomposed. Have been. For example, JP-A-8-99018, US DOE Report LA-UR-90-3159, LA-
In 12121-MS, silicon carbide was heated by microwave
It has been recognized that by heating to about 0 ° C. and injecting an organic halogen compound or the like, hydrogen chloride and carbon dioxide are rapidly decomposed. This method is suitable for high-concentration decomposition treatment such as treatment of harmful organic substances, but is not suitable for an aqueous system containing a large amount of water because a large amount of energy is required. Also,
A method in which harmful organic substances are adsorbed on activated carbon and activated carbon layers supporting copper and chromium, and then microwaved to decompose by heating to about 400 ° C (US DOE Report DOE-HWP-2
8, AD Report AD-A-253631) has been reported. It is a method of adsorbing harmful substances in a gas to water vapor and then decomposing it by microwave irradiation, and is not suitable for continuous decomposition and decomposition of harmful substances in an aqueous solution.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to develop a closed system which is milder, that is, a low-temperature, low-pressure, energy-saving, continuous and highly safe system. It is another object of the present invention to provide a method for efficiently decomposing and detoxifying an organic halogen compound in an organic solvent such as an oil from a decomposition of a harmful organic halogen compound in a high-concentration solution. .

[0006]

Means for Solving the Problems When an organic halogen compound and an aqueous alkali solution are mixed, and the mixture is irradiated with microwaves and treated at a temperature higher than the boiling point (180 ° C. or lower) and a pressure lower than 10 atm, the organic halogen compound is decomposed. It was found that the generated hydrogen chloride was trapped by the alkali and rendered harmless. However, in the case of the batch method, when a gas phase and a liquid phase are present, the solution is boiled by heating, and a harmful halogen compound evaporates in the gas phase, so that it is difficult to perform 100% treatment.

As a result of intensive research in such a situation, an organic halogen compound or a solution containing an organic halogen compound and an alkaline aqueous solution are mixed and continuously fed to a reaction section. By irradiating the microwave while continuously adjusting the output, it is continuously processed under the solvothermal condition of heating and pressurizing without boiling, and is cooled to room temperature. We found that it could be made harmless. In the present invention, a harmful organic compound and a solution containing the same are mixed with an aqueous alkali solution, continuously injected into a reaction apparatus, and continuously decomposed and irradiated under a condition of heating and pressurizing to a temperature equal to or higher than a boiling point by irradiating a microwave. The subject matter is a microwave-solvothermal continuous treatment method for harmful organic compounds, which is characterized by detoxification.

Further, it has been found that by using a catalyst such as titanium oxide in the reaction section, the treatment can be carried out efficiently at lower temperature and pressure. As the catalyst, in addition to titanium oxide, oxides such as iron oxide, copper oxide, alumina, and manganese oxide and their composite oxides, and composite materials in which the oxide is supported on a porous material such as activated carbon and clay minerals are also used. Used. The catalyst is not limited to these, but a catalyst having microwave absorption is effective. That is, the present invention provides a method of mixing a harmful organic compound and a solution containing the same with an aqueous alkali solution, and adding a microwave-absorbing and reactive-decomposing catalyst, more specifically, a metal oxide or a composite oxide thereof, to a reaction section of a reactor. Conditions for continuously injecting into a reactor equipped with a catalyst such as a composite material in which the surface of a substance or a porous substance is coated with the oxide, and heating and pressurizing to a temperature above the boiling point by microwave irradiation The present invention is directed to a continuous microwave-solvothermal treatment method for harmful organic compounds, which is continuously decomposed and made harmless.

As the microwave irradiation method, there are a method of controlling the temperature by adjusting the output under continuous irradiation and a method of controlling the temperature by adjusting the output while performing pulse irradiation. The continuous irradiation method can effectively detoxify organic chlorine compounds,
We found that pulsed irradiation was more effective and could be decomposed more efficiently. That is, the present invention provides a method of mixing a harmful organic compound and a solution containing the same with an aqueous alkali solution, and adding a microwave-absorbing and reactive-decomposing catalyst, more specifically, a metal oxide or a composite oxide thereof, to a reaction section of a reactor. To the reactor, which is loaded with a catalyst, such as a composite material or the like, on which the oxide is coated on the surface of a substance or a porous substance, and continuously or pulsedly irradiates microwaves to heat to a temperature above the boiling point. The gist of the present invention is a microwave-solvothermal continuous treatment method for harmful organic compounds, which is continuously decomposed and made harmless under pressure.

As described above, the present invention provides a technique for decomposing harmful organic compounds such as organic halogen compounds by irradiating them with microwaves under pressurized conditions to render them harmless.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Representative examples of harmful organic compounds include organic chlorine compounds such as paraffinic compounds such as dichloromethane, chloroform, carbon tetrachloride and trichloroethane, and aromatic compounds such as chlorobenzene, dichlorobenzene, PCB and dioxin. And microwave solvothermal decomposition of organic halogen compounds such as organic bromine compounds and organic fluorine compounds, but not limited thereto, and decomposition and harmlessness of harmful organic compounds such as polycyclic aromatic compounds. It can also be applied to conversion.

The present invention is applied not only to waste of harmful organic compounds such as organic halogen compounds, wastewater and waste oil containing harmful organic compounds, but also to detoxification of fly ash and the like in incinerators.
A mixture of a waste liquid containing a harmful organic compound such as an organic halogen compound and an alkaline aqueous solution, or both solutions are continuously fed to the reaction section under a pressure of not boiling (temperature: 1).
20 to 180 ° C, pressure: several to 10 atm, residence time:
(Several minutes to several tens of minutes). Microwave irradiation is effective with continuous irradiation, but pulse irradiation is more effective.

The concentrated waste liquid of the organic halogen compound and the alkaline aqueous solution are continuously mixed and sent to the reaction section, and are decomposed and made harmless by microwave irradiation. In the case of waste oil treatment containing harmful organic compounds, a powdered alkali such as sodium carbonate is mixed and sent to a microwave reactor for treatment.

The organic chlorine compound is decomposed and detoxified by microwave heating in an aqueous alkali solution, but in the case of a concentrated waste liquid, the residence time must be lengthened in order to reduce the wastewater to below the standard. By adding a catalyst such as titanium oxide, it can be efficiently decomposed and made harmless in a short time. As a method for adding a catalyst, a powdery material is suspended in a solution and subjected to a liquid sending process, and then a method of separating and separating, a granular, fibrous, and a honeycomb-shaped filled reaction tube are installed in a microwave irradiation device, The reaction solution is fed for processing.

[0015]

Next, the present invention will be described based on examples.
The present invention is not limited by the embodiments.

EXAMPLE 1 The microwave-solvothermal continuous reactor produced as a trial is an oven type device having a microwave output of 1.5 kW. The reaction part was a pressure-resistant glass tube (pressure-resistant: 10 atm), and a glass tube-cooler was attached to the upper part of the oven, and a fraction collector was attached to the top of the cooler to separate the effluent. The volume of the reaction section is 100 ml, and the volume of the entire system including the water pipe, the reaction section, and the cooling section is 400 ml. The maximum output of the microwave is 1.5 kW, pulse irradiation can be performed in addition to continuous irradiation, and the pulse interval can be set freely. Dichloromethane was dissolved in a 1N aqueous sodium hydroxide solution in this reactor, and a 100 ppm sample solution was prepared.
Microwave treatment was performed under the conditions of 0%, a temperature of 180 ° C., and a pressure of 10 atm while changing the flow rate. Flow rates are 20ml / min and 5ml / m
In, the residence time in each reaction zone is 5 minutes and 20 minutes. The results obtained are shown in FIG. Equipment volume (40
(0 ml) flowed out, the concentration in the effluent was 2 ppm for a residence time of 5 minutes, and 0.2 ppm or less for a residence time of 5 minutes, and the decomposition rates reached 98% and 99.8% or more. It was found that the decomposition can be performed at a lower reaction temperature than the conventional hydrothermal decomposition method (250 ° C.).

Comparative Example 1 A sample solution of dichloromethane (100 pp) was placed in a batch reaction vessel.
m) 100 ml was filled, and a microwave irradiation treatment was performed at a reaction temperature of 150 ° C., 4 atm, 180 ° C., and 10 atm for a predetermined time. After the reaction is completed, the residual concentration in the reaction solution is
It was analyzed by GC-MS. As a result, as shown in Table 1 and FIG. 2, in the continuous method, when the reaction temperature was 150 ° C. and the residence time was 20 minutes, the residual concentration was 0.2 ppm or less of the wastewater standard, and the decomposition rate was 99.8%. In the batch method, the decomposition rate was 75% at 150 ° C, and even at 180 ° C, the residual concentration was 10 ppm in 20 minutes, and the decomposition rate was only 90%.

[0018]

[Table 1] ──────────────────────────────────── Batch type (5 minutes) Batch type (20 minutes) Min) Continuous (20 min) ──────────────────────────────────── Reaction temperature (150 ℃) Decomposition rate 61 75 99.8 Reaction temperature (180 ° C) Decomposition rate 80 90 99.8 ────────────────────────────── ──────

Example 2 The effects of reaction temperature and residence time on the microwave-solvothermal continuous decomposition of dichloromethane were investigated. The aqueous solution of dichloromethane sample was continuously sent to the reaction section of the microwave irradiation device. Dichloromethane concentration: 100 ppm,
1000 ppm, sodium hydroxide concentration: 0.5, 1N,
Reaction temperature 120, 150, 170 ° C, residence time 10, 2
The experiment was performed under the conditions of 0 and 30 minutes. In this experiment, treatment was carried out under a slightly pressurized condition so as not to cause boiling during the reaction. Tables 2 and 3 show the results of measuring the concentration when the outflow amount was about 1.5 times the volume of the liquid sending section, reaction section, and cooling section, and calculating the decomposition rate.
Shown in Even at a reaction temperature of 120 ° C., dichloromethane was decomposed by 93% or more in a residence time of 20 minutes. In this experiment, the alkali concentration was 0.5N to 1N and the residence time was 20 minutes to 30 minutes.
Minutely, there is no significant difference in the decomposition rate.
It could be decomposed by 00%. Decomposition rates were almost equal even at sample concentrations of 100 ppm and 1000 ppm.

[0020]

Table 2 Decomposition rate of dichloromethane (dichloromethane concentration
100ppm)

[0021]

Table 3 Decomposition rate of dichloromethane (dichloromethane concentration
(1000ppm)

Example 3 100 ml of a 100 ppm sample solution of dichloromethane (Na
OH1N) was charged into a batch-type reaction vessel, and a clay mineral formed into a tube in which titanium dioxide was deposited on the surface by a sol-gel method was charged, followed by microwave irradiation to determine the decomposition rate of dichloromethane. Table 4 shows the results. It was recognized that the addition of the catalyst improved the decomposition rate by about 20%.

[0023]

Table 4 Effect of catalyst addition

Example 4 A 1000 ppm sample solution of dichloromethane was continuously fed into a reactor so that the residence time was 10 minutes, and pulse irradiation of microwaves was performed continuously or at an interval of 2 seconds to perform pulse irradiation for decomposition of dichloromethane. The effect was investigated. The experiment was performed under the conditions of a NaOH concentration of 1 N, a reaction temperature of 120 ° C., and a pressure of 10 atm. As shown in FIG. 3, the pulse irradiation had a higher decomposition rate and the residual concentration was significantly lower.

Example 5 An aqueous alkaline solution (NaOH: 1N) of 100 ppm of trichloroethylene (CHCl = CCl ₂ ) was continuously fed to the reaction section.
Microwave continuous irradiation treatment was performed while changing the flow rate. As a result, even at 120 ° C., as shown in FIG.
Minutes, the decomposition rate reached 99.2%.

[0026]

As described above, according to the present invention, according to the microwave-solvothermal continuous reaction treatment,
It is clear that organochlorine compounds such as dichloromethane and trichloroethylene are easily decomposed at low temperature and low pressure. The feature of the method of the present invention is that it is a continuous reaction treatment method,
The reaction is carried out by continuously or preferably irradiating a microwave with a catalyst, if necessary, in the reaction section, which is a processing method suitable for practical use. In the experiment of the present invention, 12
A verification test was performed under the conditions of 0 to 180 ° C., 10 atm, and an alkali concentration of 0.5 to 2 N. However, the present invention is not limited to this. It is needless to say that the concentration can be reduced, but it is considered that high-speed decomposition treatment is possible by adding a catalyst and irradiating a pulse even under conditions of low temperature and low pressure.

[Brief description of the drawings]

FIG. 1 is a drawing explaining the result of continuous decomposition of dichloromethane in Example 1.

FIG. 2 is a diagram illustrating the results of batch processing of dichloromethane in Comparative Example 1.

FIG. 3 is a drawing for explaining an irradiation effect of a MW pulse.

FIG. 4 is a view for explaining the result of decomposition of trichlorethylene by the MW-ST method.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C02F 1/02 B09B 3/00 ZAB 1/30 304G (71) Applicant 599073917 Kagawa Prefectural Industrial Technology Promotion Foundation Takamatsu, Kagawa 2217 43 Ichibayashi-cho (72) Inventor Shunsaku Kato 958-3 Hatada, Oaza, Ayanami-cho, Aya-gun, Kagawa Prefecture 500 No.2, Kawashima Higashicho, Takamatsu City, Kagawa Prefecture Room 305, Hosoya Mansion Room (72) Inventor Kaoru Tada 700, Ohonmachi, Okawa-machi, Okawa-gun, Kagawa Prefecture F-term (reference) 2E191 BA12 BA15 BC01 BD11 BD13 BD17 4D004 AB06 AB07 AC04 CA22 CB02 CB33 CC09 CC12 4D034 AA26 CA04 4D037 AB14 BA16 BB09 4G075 AA01 AA37 BA05 BA06 CA02 CA26 CA65 CA66

Claims (4)

[Claims] 1. A harmful organic compound and a solution containing the same are mixed with an aqueous alkali solution, continuously injected into a reactor, and continuously decomposed under microwave irradiation to heat and pressurize to a temperature above the boiling point. -A microwave-solvothermal continuous treatment method for harmful organic compounds, characterized by detoxification. 2. The continuous microwave-solvothermal treatment method for harmful organic compounds according to claim 1, wherein a microwave-absorbing and reactive-decomposable catalyst is loaded in the reaction section of the reactor. 3. The catalyst according to claim 1, wherein the catalyst is a metal oxide or a composite oxide thereof, or a composite material obtained by coating the surface of a porous material with the oxide.
Microwave-solvothermal continuous treatment method for harmful organic compounds. 4. The continuous microwave-solvothermal treatment method for harmful organic compounds according to claim 1, 2 or 3, wherein the microwave is continuously or pulse-irradiated.