JP5059841B2 - Dechlorination method for aromatic chlorine compounds - Google Patents

Description

  The present invention relates to a method for removing chlorine from aromatic chlorinated compounds such as PCBs, which are regarded as a global environmental pollutant, and more particularly, simple, less dangerous, economical and even under mild conditions. The present invention relates to a method for dechlorination of aromatic chlorine compounds in which the reaction is completed.

  Polychlorinated biphenyl (PCB) is an environmental pollutant that is hardly degradable, highly accumulative, and extremely toxic. As a method of treating the PCB, a method of incineration at a high temperature of 1100 ° C. or higher is recognized in Japan, but it has not been implemented so much because the consent of residents around the incineration site cannot be obtained. Since enormous amounts of PCBs have been stored in domestic affiliated companies since their use was restricted in 1972, it has been pointed out that waste PCBs may flow out due to accidents, etc., leading to serious environmental pollution. .

  Therefore, in recent years, as a method for decomposing PCB other than the high temperature incineration treatment method, (1) alkali catalytic decomposition method, (2) chemical extraction decomposition method (DMI / NaOH method), (3) t-BuOK method, ( Various methods such as 4) catalytic hydrogen dechlorination, (5) supercritical water oxidation, and (6) sodium metal method have been proposed.

  However, methods other than the above (4) require reaction conditions such as high temperature, high pressure, or strong alkali, so that the apparatus is expensive. Further, in the catalytic hydrogen dechlorination method of (4), since the dechlorination reaction is incomplete, it is necessary to use other methods (1) to (5) in combination.

  That is, in the catalytic hydrodechlorination method, PCB is diluted with a paraffinic solvent and subjected to hydrodechlorination reaction by contact with hydrogen gas in the presence of a palladium-carbon (Pd / C) catalyst. This is a method of removing chlorine as hydrogen chloride. In this method, a certain amount of dechlorination proceeds even at room temperature and normal pressure, but the reaction stops halfway and the reaction is not completed. There are various causes for this, but it is considered that one of the causes is that hydrogen chloride produced by dechlorination inhibits the reaction by corroding Pd. Thus, PCB could not be decomposed economically and sufficiently by any method.

  Accordingly, an object of the present invention is to provide a method for dechlorinating an aromatic chlorine compound that is simple, less dangerous, economical, and complete even under mild conditions.

In order to achieve the above object, the invention according to claim 1 is the hydrodechlorination by diluting an aromatic chlorine compound with a chain alcohol (excluding methanol) and contacting with hydrogen gas in the presence of a metal catalyst. An aromatic chlorine compound dechlorination method for removing chlorine from the aromatic chlorine compound by performing a reaction,
The aromatic chlorine compound is PCB, dioxin, or DDT,
The metal catalyst is Pd / C;
The hydrodechlorination reaction is characterized in that it is carried out at room temperature and normal pressure after adding ammonia or amine as an additive.

  The present applicant has found that the addition of ammonia or amine to the catalytic reduction system using Pd / C promotes the hydrodechlorination reaction of aromatic chlorine compounds such as PCB, dioxin, or DDT. Although this mechanism is still unclear, the formation of hydrogen chloride is a problem in the above-mentioned catalytic hydrogen dechlorination method. Therefore, ammonia or amine isolates hydrogen chloride from the reaction system or neutralizes hydrogen chloride. Conceivable.

In the present invention, the hydrodechlorination reaction of the aromatic chlorine compound is carried out at room temperature and normal pressure after addition of ammonia or amine, so that the hydrodechlorination reaction is favorably promoted and mild such as normal temperature and normal pressure. Dechlorination can be completed even under mild conditions. Moreover, as the above-mentioned additives, those that are common in daily life can be used, and they are not strong alkalis. For this reason, a special apparatus is not required as an apparatus for carrying out the method of the present invention. For example, a general reaction kettle and a hydrogen cylinder need only be prepared. Therefore, the dechlorination method of the aromatic chlorine compound of the present invention is simple, less dangerous, economical, and can complete the dechlorination reaction even under mild conditions. In addition, when a chain alcohol is used as the solvent, the hydrodechlorination reaction is promoted particularly well. This is presumably because the hydrochloride of the additive does not precipitate in the chain alcohol, so that the hydrochloride can be prevented from precipitating and adhering to the metal catalyst. In the present invention, since the chain alcohol is used as the solvent, in addition to the above effects, the dechlorination reaction can be completed more satisfactorily. In addition, when an expensive substance such as Pd is used as the metal catalyst, the hydrochloride does not adhere to the metal catalyst, so that it can be easily recovered and the economy can be further improved.
Can be made.

The invention described in claim 2 is characterized in that, in addition to the structure described in claim 1, the additive is triethylamine.
In the present invention, triethylamine is used as the additive. Triethylamine promotes the hydrodechlorination reaction on PCBs particularly well. Triethylamine is a substance that is extremely common in daily life, and is inexpensive and readily available. Therefore, in the present invention, in addition to the effect of the invention described in claim 1, there is an effect that it is more economical and the dechlorination reaction can be completed more satisfactorily. In addition, since the present invention is also applied to a pollutant such as PCB, which is extremely difficult to treat, the effect of the present invention becomes more prominent.

It is a chart showing the change of GC-Mass at the time of Pd / C use of 3 weight%. It is a chart showing the change of GC-Mass at the time of 10 weight% Pd / C use. It is a chart showing the change of GC-Mass when Pd / C is not used.

  Next, the embodiment of the present invention will be described with reference to specific examples. In the following examples, an experiment was conducted on ACROL 1254 and ACROL 1248 as PCBs, but other PCBs, other aromatic chlorine compounds such as dioxin and DDT were similarly removed. It can be chlorinated.

In a 100 ml eggplant-shaped flask, Akrol 1254 (5.00 g, 15.32 mmol) and triethylamine (9.23 g = 12.70 ml, 91.21 mmol) were dissolved in methanol (50 ml) to obtain 10% as a metal catalyst. Add Pd / C (0.15 g, 3 wt%). While stirring the solution, the reaction vessel is deaerated with an aspirator, and a catalytic reduction device filled with hydrogen is attached. After stirring at room temperature for 6 hours, the metal catalyst is filtered off using celite. The filtrate is concentrated under reduced pressure, water (50 ml) is added to the residue and extracted with ether (80 ml). The ether layer is washed with water (50 ml) and saturated brine (50 ml), dried over MgSO ₄ and concentrated in vacuo to give 2.27 g (96.1%) of pure biphenyl. When the aqueous layers are combined and concentrated under reduced pressure, 10.17 g (97.2%) of triethylamine hydrochloride is obtained. The reaction formula of the above reaction is shown below.

  Next, FIG. 1 (A) represents a GC-Mass chart of the Akrol 1254 before the reaction, and FIG. 1 (B) represents a GC-Mass chart in the solution after the reaction. As shown in FIG. 1 (B), nothing is confirmed from the solution after the reaction except for the biphenyl peak around 4.8 minutes. In other words, it can be seen that the concentration of Acurol 1254 was lowered to 0.5 ppm or less, which is the detection limit of GC-Mass, by the hydrodechlorination reaction.

  Further, FIG. 2 is a chart in which the amount of Pd / C used is increased to 10% by weight and the change in GC-Mass is tracked, (A) shows the start time, (B) shows 15 minutes later, C) represents after 30 minutes, and (D) represents after 60 minutes. As described above, when the amount of Pd / C used was 10% by weight with respect to the substrate, the reaction was completed in 1 hour, and the concentration of Acrol 1254 was lowered to 0.5 ppm or less of the detection limit.

  Further, Acryol 1248 could be dechlorinated in exactly the same manner. As shown in the following reaction formula, the hydrodechlorination reaction was continued for 24 hours in this experiment, but the actual reaction is considered to be completed within one hour.

  As described above, in the dechlorination method of this example, the hydrodechlorination reaction of PCB is carried out by adding triethylamine. Therefore, the hydrodechlorination reaction is favorably promoted, and a mild temperature such as normal temperature and normal pressure is obtained. Dechlorination can be completed even under conditions. Although this mechanism is still unclear, it is thought that triethylamine sequesters hydrogen chloride from the reaction system or neutralizes hydrogen chloride because the formation of hydrogen chloride becomes a problem in the conventional catalytic hydrogen dechlorination method. . Moreover, triethylamine is common in daily life and is not a strong alkali. For this reason, the dechlorination method of a present Example can be implemented with the above general apparatuses.

  Further, when the dechlorination method of this embodiment is industrially implemented, for example, if 1 kg of PCB is processed, a 15 to 20 l general reaction kettle, a well-known stirring device, and a hydrogen supply What is necessary is just to prepare the hydrogen cylinder as a device, 7-10 l of methanol, and triethylamine. Therefore, in the dechlorination method of the present example, dechlorination of PCB can be completed even under mild conditions that are simple, less dangerous, economical and mild.

  In the experiments conducted by the present applicant, it has been found that PCBs containing mineral oil can be similarly dechlorinated. Further, it has been found that PCBs actually used in the capacitors shown in Table 1 can also be dechlorinated, and can be put into practical use immediately. That is, in the dechlorination method of this embodiment, not only a pure PCB but also a PCB actually used can be dechlorinated.

  Next, the experimental conditions were variously changed and the difference in effect was considered. In the following discussion, it has been verified that even if it is not included in the scope of rights of the present invention, there is a temporary effect, but the present invention is limited to those within the scope of the above claims, and It goes without saying that various forms can be implemented without departing from the scope.

(1) Consideration about solvent The influence of the solvent to be used is largely reflected in the hydrodechlorination reaction. Particularly good results were obtained when alcohol-based solvents (MeOH, EtOH, i-PrOH, etc.) were used. This is presumably because the hydrochloride salt of an additive such as triethylamine does not precipitate in the chain alcohol, so that the hydrochloride salt can be prevented from precipitating and adhering to the metal catalyst. In addition, when an expensive substance such as Pd is used as a metal catalyst, if an alcohol solvent is used, the hydrochloride does not adhere to the metal catalyst, so that the recovery is facilitated and the economy is further improved. Can do.

(2) Consideration regarding additives The reaction was completed even when ammonia, methylamine, aniline, dimethylaniline, DBU, trimethylamine, diisopropylethylamine, NaOH or the like was used as an additive instead of triethylamine. However, without the additive, as described in the problem to be solved by the invention, a certain amount of dechlorination proceeds, but the reaction is not completed. FIG. 3 is a CG-Mass chart after 24 hours when hydrodechlorination reaction is performed using 10% Pd / C without additives. As shown in FIG. 3, in this reaction, a certain amount of dechlorination proceeds and the peak is slightly shifted to the left side, but PCB has not been removed. Further, when pyridine or quinoline was used as an additive, dechlorination was inhibited rather than proceeding, and the reaction did not proceed at all. Therefore, it is considered that aromatic bases are not suitable as additives.

  The applicant of the present application observed the progress of dechlorination using 4-chlorodiphenyl instead of PCB in order to compare and examine the difference in the effect of each additive in more detail. The reaction formula and the ratio of products are shown below.

  In the experiment, 1.2 equivalents of base (or acceptor) and 10% Pd / C were added to 4-chlorodiphenyl (100 mg), and contacted at room temperature and normal pressure (balloon) in MeOH (10 ml). Reduction was performed. After a certain period of time, 1 ml of the reaction suspension was extracted with a syringe, the catalyst was filtered, and the mixture was separated with 10 ml of hexane (for residual agricultural chemical test) and water. After the hexane layer was washed with brine and dried, another 1 ml was extracted from this with a pipette, made up to 20 ml, and the progress of the reaction was confirmed by CG-Mass. In addition, analysis by H-NMR was also performed to double check the progress of the reaction.

  From the above experimental results, it was found that, in addition to triethylamine, methylamine, aniline, DBU, trimethylamine, and N, N-diisopropylethylamine also promote the hydrodechlorination reaction very well. It is considered that this tendency is similarly observed for PCBs such as ACROL 1254 and ACROL 1248.

(3) Consideration about reaction temperature The experiment similar to the above regarding PCB was performed on the conditions of reflux heating in methanol, and -20 degreeC conditions other than room temperature. The reaction did not proceed at all under conditions of reflux heating in methanol. At −20 ° C., the reaction proceeded very slowly.

(4) Consideration regarding catalyst amount When using 10% Pd / C as a metal catalyst in an amount of 3 to 10% by weight based on the substrate, good results are obtained. As described above, when 3% by weight is used, it takes 5 to 6 hours to complete the reaction, and when 10% by weight is used, 1 hour is required to complete the reaction. Since Pd is an expensive substance, an appropriate use amount may be selected depending on whether the use amount should be saved or the reaction time should be shortened.

(5) Consideration about metal catalyst Although experiment was not carried out other than 10% Pd / C, it is considered that 1% to 30% of Pd / C can be used.

(6) Consideration regarding aromatic chlorine compounds Generally speaking, PCB is a mixture of many derivatives, but the fact that Acryol 1254 and Acryol 1248 could be rapidly dechlorinated is that almost all isomers are similarly dechlorinated. It is considered possible.

(7) Consideration on the concentration of acrole The above experiment was mainly carried out at an acrole concentration of about 10% (relative to MeOH), but it was found that the reaction proceeds even at a maximum concentration of 40%. For this reason, it has been found that the dechlorination method of the present invention can be sufficiently applied to the treatment of high-concentration PCBs.

Claims (2)

Aromatic chlorine compounds are diluted with chain alcohols (excluding methanol) and subjected to hydrodechlorination by contact with hydrogen gas in the presence of a metal catalyst to remove chlorine from the aromatic chlorine compounds. A method for dechlorination of aromatic chlorine compounds,
The aromatic chlorine compound is PCB, dioxin, or DDT,
The metal catalyst is Pd / C;
A method for dechlorination of an aromatic chlorine compound, wherein the hydrodechlorination reaction is carried out at room temperature and pressure after adding ammonia or an amine as an additive.   2. The method for dechlorination of an aromatic chlorine compound according to claim 1, wherein the additive is triethylamine.

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