JP3678738B2 - Method for dechlorination of polychlorinated biphenyls - Google Patents

Description

  The present invention relates to a method for dechlorinating polychlorinated biphenyl (hereinafter sometimes abbreviated as PCB) to render it harmless.

  Among various halogenated organic compounds, PCB is extremely harmful to living organisms including the human body. Therefore, it was designated as a specific chemical substance in 1973, and its manufacture, import and use are prohibited. However, after that, tens of thousands of tons of PCBs are left untreated without determining an appropriate disposal method. PCB decomposes PCB safely technically because chlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF), which are highly toxic dioxins, are by-produced at high temperature (30 to 750 ° C) decomposition. This is difficult, and various safe and efficient decomposition methods for PCBs have been studied for many years.

  For example, Japanese Patent Laid-Open No. 2001-19646 discloses harmful organic chlorine compounds by irradiating microwaves while blowing hydrogen gas into a mixed system containing activated carbon supporting platinum and an aromatic chlorine compound (parachlorophenol). Has been proposed (see Patent Document 1).

  JP-A-6-25691 discloses a hydrocarbon oil containing a small amount of a halogenated aromatic compound (recovered trans oil containing PCB) and 1,3-dimethyl-2-imidazolidinone (DMI) as a solvent. In addition, a method of removing a halogenated aromatic compound by separating hydrocarbon oil after heating at 100 ° C. to 300 ° C. in the presence of an alkaline substance such as sodium ethoxide or NaOH has been proposed (patent) Reference 2).

  On the other hand, JP-A-8-266888 proposes a method in which an aromatic halogen compound is decomposed by heating to 30 to 100 ° C. in the presence of a decomposition catalyst and an alkali compound in a second alcohol ( (See Patent Document 3).

  Furthermore, in Japanese Patent Laid-Open No. 4-202500 (Patent No. 1982066), a base metal catalyst such as a zeolite / nickel catalyst is added to an electrical insulating oil containing an organic chlorine compound, and the heating gas is heated in a hydrogen gas atmosphere. A method for dechlorination by hydrogenation has been proposed (see Patent Document 4).

  Among the above technologies, Patent Documents 1 and 3 are technologies related to dechlorination of 100% organic chlorine compounds, and Patent Documents 2 and 4 are technologies related to dechlorination of insulating oils containing organic chlorine compounds, The detoxification technology for harmful organic chlorine compounds is roughly divided into the former high concentration system and the latter low concentration system. As the latter technique, recently, Japanese Patent Application Laid-Open No. 2004-34015 discloses that a capacitor, a transformer, or the like containing PCB is placed in a high-frequency induction heating furnace together with a heat generation promoting substance such as an alkali compound, an aluminum piece, or a carbon piece. A method of detoxifying PCB by blowing an inert gas such as the above into a heating furnace and heating to 1000 ° C. or more in an oxygen-free atmosphere has been proposed (see Patent Document 5).

  Japanese Patent Application Laid-Open No. 2004-141815 proposes a method for dehalogenating an alkali metal dispersion, an organic halogen compound, and a hydrogen donor in a microchannel (fine channel) of a reactor. (See Patent Document 6). In this method, when PCB is dechlorinated with Na dispersion, Na particles and polymer products are present in the microchannel of the reactor, preventing the phenomenon of clogging the flow path, and no complicated temperature control is required. Therefore, it can be said that it is an excellent method in that it can be dehalogenated in an energy-saving and space-saving manner, and can also be processed at the transformer storage site.

JP 2001-19646 A (Claim 1, paragraph number 0009) JP-A-6-25691 (Claim 1, Claim 5, Paragraph No. 0004, Table 3 on page 3, Paragraph No. 0011, etc.) JP-A-8-266888 (Claim 1, paragraph number 0011, etc.) JP-A-4-202500 (page 2, lower right column, line 7 to page 3, upper left column, line 8, etc.) JP 2004-34015 A (Claim 1, page 2, lines 46 to 48, page 3, lines 31 to 49, etc.) JP 2004-141815 A (Claim 1, test examples of paragraph numbers 0134 to 0136, etc.)

  However, in the methods described in JP-A-2001-19646 and JP-A-4-202500, it is necessary to supply hydrogen gas from the outside to a reaction system containing an aromatic chlorine compound, and an explosion-proof device is also required. Therefore, it is not preferable as a practical method. Further, the solvent DMI used in the method described in JP-A-6-25691 is as expensive as 2000 yen / kg, and in this method, the residual PCB ratio is large, and a reaction is required for sufficient dechlorination. Since it is necessary to lengthen the time, it is not suitable for mass processing of PCBs.

  On the other hand, in the method described in JP-A-8-266888, since the PCB-containing solution is thermally decomposed under reflux conditions (78 ° C.), the reaction rate is slow, so that by-products may be generated. No mention is made of a method for decomposing PCBs that are mixed in a small amount in insulating oil in a pole transformer.

  The method described in Japanese Patent Application Laid-Open No. 2004-34015 eliminates the need for an extraction work step from the disassembly of the PCB-containing electrical device, and thus eliminates the need for a detoxification treatment step for containers and internal components that have been in contact with the PCB insulating oil. However, the high-frequency induction heating furnace is brought to a high temperature of 1500 ° C. and induction heating of aluminum and iron internal parts, which are condenser containers, is carried out and melted in an instant. Therefore, it is difficult to say that the PCB can be easily detoxified at a site such as a transformer storage.

  Furthermore, the method described in Japanese Patent Application Laid-Open No. 2004-141815 has a problem in that it needs to be handled with care because it uses metallic Na, and a special reactor needs to be newly installed.

  Therefore, it is desired to develop a method that can perform a large amount of processing safely and quickly, and that can be decomposed at low cost.

  Therefore, the present invention has been made in view of the above-mentioned conventional problems, and a large amount of polychlorinated biphenyl mixed in a trace amount in insulating oil in a pole transformer that is difficult to dechlorinate safely and quickly. An object of the present invention is to provide a dechlorination method that can be dechlorinated and detoxified, and can be practically used at a lower cost.

  As a result of intensive studies to solve the above problems, the present inventors have mixed an organic hydrogen donor with an insulating oil containing a trace amount of polychlorinated biphenyl, and in the presence of an alkali compound and an inorganic catalyst, It has been found that the polychlorinated biphenyl can be dechlorinated without supplying hydrogen and heat from the outside, and the present invention has been completed.

  That is, the present invention is characterized in that a hydrogen donor is mixed with an insulating oil containing a trace amount of polychlorinated biphenyl and dechlorinated by irradiation with microwaves in the presence of an alkali compound and an inorganic catalyst. A method for dechlorination of polychlorinated biphenyls is provided. According to the present invention, PCB can be dechlorinated without supplying hydrogen and heat from the outside, and therefore, a large amount of PCB can be dechlorinated and detoxified quickly and safely at low cost. . Furthermore, since it can be dechlorinated without supplying hydrogen from the outside, it does not require a high-temperature and high-pressure reaction vessel and can be decomposed at normal pressure.

  The polychlorinated biphenyl content in the insulating oil is preferably 50 ppm or less, more preferably 20 ppm or less, and even more preferably 5 ppm or less. This is because most of the insulating oil containing PCB has a PCB content of 50 ppm or less and can be decomposed in a shorter time as the PCB content decreases.

  In the dechlorination method of the present invention, the addition amount of the hydrogen donor is preferably 10 to 50% by mass (with respect to insulating oil), and the content of the alkali compound is 0.001 to 5.0% by mass. It is preferable that the content of the inorganic catalyst (with respect to insulating oil) is 0.001 to 30% by mass (with respect to insulating oil). An aromatic hydrocarbon may be further added to the insulating oil.

  Moreover, it is preferable that the reaction temperature at the time of dechlorination is 50-200 degreeC.

  In the polychlorinated biphenyl dechlorination method, the hydrogen donor is at least one compound selected from the group consisting of heterocyclic compounds, amine compounds, alcohol compounds, ketone compounds and alicyclic compounds. It is preferable that Among the hydrogen donors, the use of one or a mixture of two or more of these organic hydrogen donors can increase the dechlorination efficiency of polychlorinated biphenyls.

  In the polychlorinated biphenyl dechlorination method, the alkali compound is preferably at least one compound selected from the group consisting of caustic soda, caustic potash, sodium alkoxide, potassium alkoxide, and calcium hydroxide. By using one or two or more of these compounds among the alkali compounds, the dechlorination efficiency of PCB can be increased.

  In the polychlorinated biphenyl dechlorination method, the inorganic catalyst is preferably at least one compound selected from the group consisting of a carbon crystal compound and a metal-supported carbon compound. By using one or more of these compounds among inorganic catalysts, the dechlorination efficiency of PCB can be increased.

  As described above, according to the present invention, a hydrogen donor is added to an insulating oil containing a trace amount of PCB, and microwaves are irradiated in the presence of an alkali compound and an inorganic catalyst, whereby a high-temperature and high-pressure reaction vessel is formed. Since it can be decomposed at normal pressure in a short time without need, a large amount of insulating oil in the pole transformer can be dechlorinated at low cost.

  Moreover, since a high temperature / high pressure reaction is not performed, there are few side reaction products. Therefore, since a large amount of PCB can be detoxified on a practical scale, its practical value is great.

  The PCB dechlorination method of the present invention is to dechlorinate by mixing a hydrogen donor with insulating oil containing a small amount of PCB and irradiating with microwaves in the presence of an alkali compound and an inorganic catalyst. It is a feature. Details of the present invention will be described below.

  The polychlorinated biphenyls that are the subject of the present invention include compounds in which a chlorine atom is substituted in the biphenyl compound, and the number of substituted chlorine atoms is 1 to 10. The average number of substituted chlorine atoms is generally 2-6. In the present invention, at least one selected from these polychlorinated biphenyls can be used, and each can be used alone or in combination of two or more.

  In general, polychlorinated biphenyls do not exist as a single compound but exist as a mixture having different numbers of chlorine atoms and different substitution positions. Therefore, there are 209 isomers based on the combination of the number of chlorine atoms and the substitution position, and more than 100 isomers exist in the commercial product.

  For example, as a coplanar PCB, 3,4,4 ′, 5-tetrachlorobiphenyl, 3,3 ′, 4,4′-tetrachlorobiphenyl, 3,3 ′, 4,4 ′, 5-pentachlorobiphenyl, 3,3 ′, 4,4 ′, 5,5′-hexachlorobiphenyl, 2,3,3 ′, 4,4′-pentachlorobiphenyl, 2,3,4,4 ′, 5-pentachlorobiphenyl, 2 3 ′, 4,4 ′, 5-pentachlorobiphenyl, 2 ′, 3,4,4 ′, 5-pentachlorobiphenyl, 2,3,3 ′, 4,4 ′, 5-hexachlorobiphenyl, 2, 3,3 ′, 4,4 ′, 5′-hexachlorobiphenyl, 2,3 ′, 4,4 ′, 5,5′-hexachlorobiphenyl, 2,3,3 ′, 4,4 ′, 5,5 ′ -Heptachlorobiphenyl and the like

  PCBs are usually marketed as a mixture of PCBs alone, and these are used for capacitors and transformers. Specific examples include KC-200 (biphenyl dichloride), KC-300 (biphenyl trichloride), KC-400 (biphenyl tetrachloride), KC-500 (biphenyl pentachloride), KC of Kaneka Chemical Co., Ltd. -600 (biphenyl hexachloride) and Arrochlor 1254 (54% Chlorine) manufactured by Mitsubishi Monsite Corporation.

As an example, the distribution (mass%) of isomers of the commercial product KC-300 is shown below.
Monochrome biphenyl slightly dichlorobiphenyl 12.10%
Trichlorobiphenyl 54.98%
Tetrachlorobiphenyl 27.05%
Pentachlorobiphenyl 4.72%
Hexachlorobiphenyl 1.08%
Heptachlorobiphenyl slightly Octachlorobiphenyl 0
Nonachlorobiphenyl 0
Decachlorobiphenyl 0

  In the present invention, the “hydrogen donor” means a compound capable of donating a hydrogen atom to a radical generated from polychlorinated biphenyl, for example, a heterocyclic compound, an amine compound, an alcohol compound. And organic hydrogen donors such as ketone compounds and alicyclic compounds. These compounds are excellent in PCB dechlorination efficiency. Among these, alcohol compounds, ketone compounds, and alicyclic compounds are preferable from the viewpoint of safety, and alcohol compounds are particularly preferable. A hydrogen donor can be used individually or in combination of 2 or more types.

  Here, examples of the heterocyclic compound include 1,3-dimethyl-2-imidazolidinone (DMI).

  Examples of the amine compound include dimethylethylenediamine.

  The alcohol compound may be either an aliphatic alcohol or an aromatic alcohol, and a monohydric alcohol or polyhydric alcohol having a linear or branched chain can be used without limitation. The carbon number of the alcohol compound is preferably in the range of 1 to 12, more preferably in the range of 2 to 9, and still more preferably in the range of 3 to 6. Specific examples of the alcohol compound include, for example, methanol, ethanol, 1-propanol, 2-propanol, n-butanol, s-butanol, t-butanol, 1-pentanol, 2-pentanol, and 3-pentanol. 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol and other aliphatic alcohols, cyclopropyl alcohol, cyclobutyl alcohol, cyclopentyl alcohol, cyclohexyl Examples thereof include alicyclic alcohols such as alcohol, cycloheptyl alcohol and cyclooctyl alcohol, and polyhydric alcohols such as ethylene glycol, propylene glycol and decalin diol.

  Among these alcohol compounds, aliphatic alcohols such as 2-propanol and alicyclic alcohols such as cyclohexyl alcohol are preferable from the viewpoint of decomposition efficiency. In particular, an alicyclic alcohol is preferred from the viewpoint of maintaining a high reaction temperature because of its high boiling point. On the other hand, an aliphatic alcohol such as 2-propanol having a relatively low boiling point is preferable from the viewpoint of improving the dechlorination efficiency even at a relatively low reaction temperature.

  Examples of the ketone compound include methyl ethyl ketone, cyclohexanone, tricyclododecanone, and the like.

  Examples of the alicyclic compound include tetralin and cyclohexane.

  The alkali compound used in the present invention can be used without limitation as long as it can accelerate the dechlorination reaction of polychlorinated biphenyl, but from the viewpoint of increasing the dechlorination efficiency, caustic soda, caustic potash, sodium alkoxide, Potassium alkoxide, calcium hydroxide and the like are preferably used. Among these, caustic soda and caustic potash are particularly preferable from the viewpoint of cost and handling properties. An alkali compound can be used individually or in combination of 2 or more types.

  The inorganic catalyst used in the present invention can be used without limitation as long as it can promote the dechlorination reaction of polychlorinated biphenyl, and the type thereof is not particularly limited. An inorganic catalyst has a long catalyst life and is stable even in the presence of an alkali compound, and thus is more preferably used than an organic catalyst. As specific examples of the inorganic catalyst, composite metal oxides, carbon crystal compounds, metal-supported carbon compounds, metal oxides, and the like are preferably used from the viewpoint of increasing dechlorination efficiency. Among these, from the viewpoint of high safety in an alkaline atmosphere, a carbon crystal compound and a metal-supported carbon compound are preferable, and a metal-supported carbon compound is particularly preferable. An inorganic catalyst can be used individually or in combination of 2 or more types.

  Here, examples of the carbon crystal compound include graphite, carbon nanotubes (both including and not including metal), fullerene, and the like.

  Moreover, as said metal carrying | support carbon compound, if it is a carbon compound which carry | supported the metal, it can be used without a restriction | limiting, The metal carrying amount is 1-20 mass% with respect to the catalyst whole quantity, More preferably, it is 5-10 mass. % Should be good. Examples of the supported metal include iron, silver, platinum, ruthenium, palladium, rhodium and the like, and palladium, ruthenium, and platinum are preferable from the viewpoint of increasing the dechlorination efficiency. Specific examples of the metal-supported carbon compound include Pd / C (palladium-supported carbon compound), Ru / C (ruthenium-supported carbon compound), and Pt / C (platinum-supported carbon compound). The particle size of the metal-supported carbon compound is preferably 75 to 300 μm. When the particle size exceeds 300 μm, the reactivity is deteriorated, and when it is less than 75 μm, the handling property is deteriorated. More preferably, 125 to 250 μm is desirable.

  The addition amount of the hydrogen donor in the present invention is preferably 10 to 50% by mass (with respect to insulating oil), more preferably 10 to 40% by mass, and still more preferably 10 to 30% by mass. If the amount added is too small, the dechlorination reaction will be insufficient. On the other hand, if the amount added is too large, the dechlorination reaction will proceed sufficiently, but by-products will be easily generated, and the economy will be poor. It becomes.

  Moreover, it is preferable that content of the alkali compound in a reaction solution is 0.001-5.0 mass% (vs. insulating oil), More preferably, it is 0.001-1.0 mass%, More preferably, it is 0. It is good that it is 0.01-0.6 mass%. When the content is too small, the dechlorination reaction does not proceed. On the other hand, when the content is too large, stirring and mixing becomes difficult.

  In the dechlorination method of the present invention, the ratio of the alkali compound / hydrogen donor / polychlorinated biphenyl is preferably 0.001 to 5/10 / 0.000001 to 10 (molar ratio). The molar ratio of the three components is more preferably 0.01 to 3/10 / 0.00001 to 5, and particularly preferably 0.02 to 2/10 / 0.0001 to 1.

  The inorganic catalyst can be dispersed in the reaction solution, brought into contact with the reaction solution in a reactor equipped with the catalyst, or a catalyst column containing the catalyst is prepared and reacted while the reaction solution is circulated through it. It can be contacted with the reaction solution. The content of the inorganic catalyst in the reaction solution is preferably 0.001 to 30% by mass with respect to the insulating oil. In the method of dispersing the inorganic catalyst in the reaction solution, the content is preferably 0.001 to 2.0% by mass, more preferably 0.01 to 1.0% by mass, and still more preferably 0.1 to 0.8%. It is good that it is mass%. When the content is too small, the amount of hydrogen generated is small and dechlorination is difficult to proceed.On the other hand, when the content is too large, stirring and mixing of the reaction system becomes difficult, which is economically disadvantageous. Become. When the catalyst is used in a column or a reactor, the amount of the inorganic catalyst is preferably 5 to 30% by mass, more preferably 10 to 30% by mass with respect to the insulating oil.

  In the dechlorination method of the present invention, a chemical such as an aromatic hydrocarbon can be added to the insulating oil containing a trace amount of PCB in addition to the hydrogen donor, the alkali compound and the inorganic catalyst. The addition of the aromatic hydrocarbon is preferable in terms of promoting the dechlorination of PCB and suppressing the increase in the viscosity of the insulating oil due to the addition of the compound. Examples of the aromatic hydrocarbon include toluene, ethylbenzene, cumene, xylene and the like. These aromatic hydrocarbons can be used alone or in any combination of two or more.

  The addition amount of the aromatic hydrocarbon is preferably 5 to 80% by mass, more preferably 5 to 50% by mass with respect to the insulating oil containing a small amount of PCB. If it is less than 5% by mass, the effect of promoting the decomposition of PCB is insufficient, and even if it exceeds 50% by mass, the effect of promoting the decomposition reaches its peak. Especially preferably, it is good to set it as 5-30 mass%.

  The output, frequency, and irradiation method of the microwave used in the present invention are not particularly limited, and may be electrically controlled so that the reaction temperature can be maintained within a predetermined range. When the output is too low, the amount of hydrogen generation is reduced, and when the output is too high, the microwave utilization rate is deteriorated, so that the range is 10 W to 20 kW while being electrically controlled, more preferably the range is 65 W to 5 kW. Is desirable. The microwave frequency is preferably 1 to 300 GHz. When the frequency range is less than 1 GHz or more than 300 GHz, the inorganic catalyst and the hydrogen donor are not sufficiently heated. More preferably, a frequency of 1 to 5 GHz is desirable. Microwave irradiation may be either continuous irradiation or intermittent irradiation.

  Further, the irradiation position of the microwave is not particularly limited as long as the catalyst in the reaction system is irradiated, but from the viewpoint of promoting the dechlorination by increasing the catalyst activity as much as possible, It is preferred to irradiate the solution.

  The reaction atmosphere is more preferably carried out in an inert gas because undesirable side reactions do not occur.

  The reaction time is preferably 0.01 minutes to 300 minutes. If it is less than 0.01 minutes, the decomposition reaction is insufficient, and if the reaction time is longer than 300 minutes, there is no practical meaning. From the viewpoint of rapid PCB mass processing, it is more preferably 5 minutes to 180 minutes, and particularly preferably 5 minutes to 120 minutes.

  The reaction temperature is preferably 50 to 200 ° C. When the reaction temperature is less than 50 ° C., the decomposition reaction becomes insufficient. On the other hand, when it exceeds 200 ° C., the dechlorination reaction proceeds sufficiently, but by-products are easily generated, and the economy is inferior. From the viewpoint of balancing the suppression of side reaction products and the PCB decomposition rate, it is more preferably 50 to 160 ° C, and particularly preferably 60 to 145 ° C.

  In the present invention, the insulation oil extracted from the transformer or the like may be filled in a separately prepared reaction tank for dechlorination, or the hydrogen donor, alkali compound and catalyst may be added directly to the transformer or the like for removal. It may be chlorinated. In the former case, a large amount of insulating oil can be efficiently dechlorinated, and in the latter case, the insulating oil adhering to the equipment can also be dechlorinated at once.

  According to the PCB dechlorination method of the present invention, the PCB itself is decomposed at a speed equal to or higher than that when hydrogen gas is blown into the reaction system from the outside. Although the mechanism is not clear, it is considered that the alkali metal radical provided from the alkali compound promotes the dechlorination reaction of PCB, and the hydrogen radical from the hydrogen donor enters therein.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited only to a following example. In the following examples and the like, “mass%” and “part by mass” are abbreviated as “%” and “part”, respectively, unless otherwise specified.

  FIG. 1 shows a schematic view of the PCB disassembling apparatus used in Examples 1-16. A three-necked flask 2 is placed in the microwave generator 1, two of the three necks are used as a nitrogen introduction port 2a and an insertion port 2b of a thermometer 3, and a Liebig cooling tube 4 is provided at the center port 2c. The reaction product is taken out of the reaction system.

(Example 1)
Experiments were performed using a simple microwave reactor temperature control type ZMW-024 manufactured by Shikoku Keiki Kogyo Co., Ltd. 0.5g of KOH flakes (95%) made by Nippon Soda as an alkaline substance and 100ml of 7 kinds of insulating oil containing 2ppm of KC-400 (biphenyl tetrachloride, Kaneka Chemical Co., Ltd.) And 20 ml of isopropyl alcohol (IPA) manufactured by Wako Pure Chemical as a hydrogen donor and 0.2 g of 80-100 mesh activated carbon (Pd / C: manufactured by Wako Pure Chemical) carrying 5% palladium as an inorganic catalyst, respectively. And introduced into a three-necked flask 2 having an internal volume of 200 ml.

  After introducing the mixture of each substance into the flask 2 and substituting the gas inside the flask 2 with nitrogen gas, the mixture was stirred with a magnetic stirrer and the temperature was maintained at 82 ° C. so that the temperature was kept constant at 82 ° C. Irradiation was performed for 60 minutes while electrically controlling the waves. Nitrogen gas was allowed to flow at 50 ml / min during the reaction.

  Since the Liebig condenser 4 is attached to the upper part of the three-necked flask 2, the isopropyl alcohol is refluxed, but the by-product acetone is carried out of the system, so that the reaction is promoted.

The isomer distribution (% by mass) of KC-400 used in the experiment is shown below.
Monochrome Robiphenyl 0.01%
Dichlorobiphenyl 0.48%
Trichlorobiphenyl 17.47%
Tetrachlorobiphenyl 51.43%
Pentachlorobiphenyl 27.92%
Hexachlorobiphenyl 2.55%
Heptachlorobiphenyl 0.14%
Octachlorobiphenyl 0%
Nonachlorobiphenyl 0%
Decachlorobiphenyl 0%

  (Composition of tetrachlorobiphenyl) 2,3,4,5-tetrachlorobiphenyl, 2,3,4,6-tetrachlorobiphenyl, 2,2 ′, 3,4-tetrachlorobiphenyl, 2,3,3 ′ , 4-tetrachlorobiphenyl, 2,3,4,4′-tetrachlorobiphenyl, 3,4,4 ′, 5-tetrachlorobiphenyl, 3,3 ′, 4,4′-tetrachlorobiphenyl, etc. Contains.

(Example 2)
PCB was decomposed by the same operation as in Example 1 except that the reaction temperature was about 82 ° C. and the reaction time was 120 minutes.

(Example 3)
The PCB was decomposed in the same manner as in Example 1 except that 0.4 g of 80-100 mesh activated carbon (Pd / C: manufactured by Wako Pure Chemical Industries) carrying 5% palladium was used as the inorganic catalyst.

(Examples 4 to 5)
PCB was decomposed by the same operation as in Example 1 except that 0.1 g and 0.05 g of KOH flakes (95%) made by Nippon Soda were ground as alkaline substances in a mortar.

(Example 6)
Experiments were performed using a simple microwave reactor temperature control type ZMW-024 manufactured by Shikoku Keiki Kogyo Co., Ltd. 0.5g of KOH flakes (95%) made by Nippon Soda as an alkaline substance and 100ml of 7 kinds of insulating oil containing 2ppm of KC-400 (biphenyl tetrachloride, Kaneka Chemical Co., Ltd.) And 20 ml of cyclohexanol manufactured by Wako Pure Chemical as a hydrogen donor and 0.2 g of 80-100 mesh activated carbon (Pd / C: manufactured by Wako Pure Chemical) carrying 5% palladium as an inorganic catalyst, The solution was introduced into a three-neck flask 2 having an internal volume of 200 ml.

  After introducing the mixture of each substance into the flask 2 and substituting the gas inside the flask 2 with nitrogen gas, the mixture was stirred with a magnetic stirrer and the temperature was maintained at 130 ° C. so that the temperature was kept constant at 130 ° C. Irradiation was performed for 120 minutes while electrically controlling the waves. Nitrogen gas was allowed to flow at 50 ml / min during the reaction. The internal temperature of the flask 2 was maintained at a temperature (130 ° C.) lower than the boiling point of cyclohexanol (164 ° C.).

(Example 7)
PCB was decomposed by the same operation as in Example 6 except that the reaction time was 60 minutes.

(Example 8)
The PCB was decomposed in the same manner as in Example 6 except that 0.4 g of 80-100 mesh activated carbon (Pd / C: manufactured by Wako Pure Chemical Industries) carrying 5% palladium was used as the inorganic catalyst.

(Examples 9 to 12)
The same operation as in Example 6 was conducted except that 0.2 g, 0.1 g, 0.05 g, and 0.01 g of KOH flakes (95%) made by Nippon Soda were ground as alkaline substances in a mortar. PCB was disassembled.

(Examples 13 to 16)
The PCB was decomposed by the same operation as in Example 6 except that the microwave frequency and irradiation energy were appropriately changed, the reaction temperature was changed between 82 and 160 ° C., and the reaction time was 120 minutes.

(Evaluation methods)
The solution before and after the reaction is subjected to Sep-Pak pretreatment and then a gas chromatography mass spectrometer QP5050 (hereinafter referred to as “GC-MS”) manufactured by Shimadzu Corporation using DB1 (manufactured by J & W Scientific) as a capillary column. ) To confirm dechlorination (decomposition rate) from the change in the PCB peak area.

  Table 1 summarizes the experimental conditions and evaluation results of Examples 1 to 16.

  From the results in Table 1, it was confirmed that the PCB disappeared by reacting at 80 ° C. to 160 ° C. for 2 hours. The longer the reaction time, the better the PCB decomposition rate.

(Example 17)
A cylindrical reaction vessel with an internal volume of 3 L provided in the microwave irradiation apparatus is equipped with 330 g of a catalyst (average particle size of about 1 mm) carrying 5% palladium (Pd) on granular activated carbon (trade name: Diahop 008). , 13.82 g of Nippon Oil Soda KOH flakes (95%) ground in a mortar as alkaline substances and 2200 ml of insulating oil 1 type 2 containing 10 ppm of KC-400 in the reaction vessel, and Wako Jun as hydrogen donor A mixture of isopropyl alcohol (IPA) (440 ml) and a mixture obtained by stirring with a 3000 rpm homomixer for 20 minutes was introduced. After introducing these, the inside of the reaction vessel was replaced with nitrogen gas, and while stirring the inside of the reaction vessel, the frequency of 2.45 GHz and the maximum output of 1.5 kW so that the liquid temperature in the reaction vessel was kept constant at 60 ° C. Irradiation was performed for 120 minutes while being electrically controlled. Nitrogen gas was allowed to flow during the reaction. The solution in the reaction vessel was cooled to 30 ° C. with a cooler installed outside the microwave irradiation apparatus, and the cooled reaction solution was returned to the reaction vessel again to circulate at a flow rate of 500 ml / min.

(Example 18)
The reaction solution was cooled to 45 ° C. with a cooler installed outside the microwave irradiation apparatus, and the liquid was circulated by an operation of returning the cooled reaction solution back into the reaction vessel, and the same as in Example 17 Dechlorination was performed by operation.

(Example 19)
A cylindrical reaction vessel with an internal volume of 3 L provided in the microwave irradiation apparatus is equipped with 600 g of a catalyst (average particle size of about 1 mm) carrying 5% palladium (Pd) on granular activated carbon (trade name: Diahop 008). In the reaction vessel, 20007 ml of seed oil No. 2 containing 50 ppm of KC-400, 12.57 g of KOH flakes (95%) made by Nippon Soda as an alkaline substance in a mortar, and Wako Jun as hydrogen donor A solution prepared by stirring 400 ml of pharmaceutical isopropyl alcohol (IPA) with a homomixer at 3000 rpm for 20 minutes was introduced. After introducing these, the inside of the reaction vessel was replaced with nitrogen gas, and while stirring the inside of the reaction vessel, the frequency of 2.45 GHz and the maximum output of 1.5 kW so that the liquid temperature in the reaction vessel was kept constant at 60 ° C. The microwave was irradiated for 180 minutes while being electrically controlled. Nitrogen gas was allowed to flow during the reaction. The solution in the reaction vessel was cooled to 30 ° C. with a cooler installed outside the microwave irradiation apparatus, and the cooled reaction solution was returned to the reaction vessel again to circulate at a flow rate of 500 ml / min.

(Evaluation methods)
The solution before and after the reaction was subjected to GC-MS, and dechlorination (PCB decomposition rate) was confirmed from the change in the PCB peak area.

  Table 2 summarizes the experimental conditions and evaluation results of Examples 17 to 19.

  From the results in Table 2, it was confirmed that PCB disappeared by reacting at 60 ° C. for 2 to 3 hours.

It is the schematic of the PCB decomposition experiment apparatus by the microwave used by the present Example.

Explanation of symbols

1 Microwave generator 2 Three-necked flask 3 Thermometer 4 Liebig condenser

Claims (9)

Dechlorination of polychlorinated biphenyls characterized by mixing a hydrogen donor with insulating oil containing a trace amount of polychlorinated biphenyls and dechlorinating by irradiation with microwaves in the presence of an alkali compound and an inorganic catalyst. Method. 2. The polychlorinated biphenyl dechlorination method according to claim 1, wherein the polychlorinated biphenyl content in the insulating oil is 50 ppm or less. The polychlorinated biphenyl dechlorination method according to claim 1 or 2, wherein the hydrogen donor is added in an amount of 10 to 50 mass% (with respect to insulating oil). The content of the alkali compound is 0.001 to 5.0% by mass (for insulating oil), and the content of the inorganic catalyst is 0.001 to 30% by mass (for insulating oil). Item 4. A method for dechlorination of polychlorinated biphenyls according to any one of Items 1 to 3. Furthermore, aromatic hydrocarbon is added, The dechlorination method of polychlorinated biphenyls in any one of Claims 1-4 characterized by the above-mentioned. The method for dechlorination of polychlorinated biphenyls according to any one of claims 1 to 5, wherein a reaction temperature at the time of dechlorination is 50 to 200 ° C. The hydrogen donor is at least one compound selected from the group consisting of a heterocyclic compound, an amine compound, an alcohol compound, a ketone compound, and an alicyclic compound. The method for dechlorination of polychlorinated biphenyl according to any one of the above. The polychlorinated biphenyl according to any one of claims 1 to 6, wherein the alkali compound is at least one compound selected from the group consisting of caustic soda, caustic potash, sodium alkoxide, potassium alkoxide, and calcium hydroxide. Dechlorination method. The dechlorination of polychlorinated biphenyl according to any one of claims 1 to 6, wherein the inorganic catalyst is at least one compound selected from the group consisting of a carbon crystal compound and a metal-supported carbon compound. Method.

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