CA1094580A - Method for the safe disposal of polychlorinated biphenyls - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The invention provides a method of disposing of polychlorinated biphenyls without causing a health hazard to the public in which the polychlorinated bi-phenyls are converted into harmless and useful compounds by the hydrogenation-dechlorination thereof.

Description

lO~J-1SRO
, The present invention relates to a method of disposing of poly-chlorinated biphenyl~ without cauqing a health hazard to the public.
More particularly, the present invention relates to a method of converting polychlorinated biphenyls into useful compounds by the hydrogenation-dechlorination thereof.
It is known in the art that polychlorinated biphenyls (hereinafter referred to as PCB) is a useful substance for a transformer oil, a capacitor oil, a heat transfer agent and a carbonless reproducing paper;
it has been in wide use for theqe applications. On the other hand, in view of the recent increased public interest to pollution problems the toxic nature of PCB has also drawn its attention, and the recovery of unused PCB has been started. However, a further problem has been brought about as to how to dispose of it without cauqing a health hazard to the public. So far many proposalq have been made for disposing of the unused PCB, such as incineration, ultraviolet--decomposition, hydro-thermal decomposition, radiololysis. However, it has been found that the disposal of it under these methods is not satisfactory. Under the incineration methods it is imposqible to consume PCB completely by fire, and additionally, it is likely to cause air contamination. Under the ultraviolet decomposition method the biphenyls and salts produced constitute a bar to the transmission of ultraviolet rays. The radiololysis methods are effective only when the PC~ to be treated is extremely diluted, and have no practical value. Lastly, under the hydro-thermal decomposition methods it is required to conduct them under the condition of elevated temperatures and high pressures (e.g. at 300C, 200atm), and the products produced through the methods are not identified, thereby making it diffic~llt to flow them away to the se~age.
The present invention aims at overcoming the difficulties of th~ ~own methods of disposing of PCB, and has for its object to provide ~r, 10~'~580 an improved method for the safe disposal of PCB, on the basis of the discovery that PCB can be converted into various useful compounds, when PCB, emulsified and d s-persed in an alkaline aqueous solution, is reacted with hydrogen in the presence of hydrogenation catalyst, wherein it has been found that these useful compounds are the by-products of the hydrogenation-dechlorination of the PCB.
Therefore, according to the present invention the disposal of PCB includes the steps of emulsifying and dispersing PCB in an alkaline aqueous solution, and reacting the same with hydrogen in the presence of hydrogenation catalyst.
The sequence of the addition of alkali, water, an emulsifyiny-dispersing agent, and PCB is not important provided the PCB is suitably emulsified and dispersed in the alkaline aqueous solution.
As described above, according to the present invention a great deal of PCB is dechlorinated and converted into various useful compounds, wherein the hydrogen chlorides produced through the reaction of PCB with hydrogen are changed into harmless salts 7 and wherein the products obtained in this way are separately collected. In addi-tion, according to the present invention there is no need for setting the condition of high temperatures and high pressures, but it is practicable under a normal condition.
The general formula of PCB is expressed as follows:

~ (1 _ m + n _ 1 0) Clm Cln E~

10~ ~80 The method of this invention is applicable either to individual compounds expressed above or to a mixture thereof.
Under the method of this invention PCB is firstly converted into biphenyl as a result of dechlorination through a hydro-dechlorinating reaction, and a part of the biphenyl is converted into bicyclohexyl - 2a -F`-109 ~S80 i through hydrogenation. In this case, it is also possible to let the reaction keep on until the whole amount of biphenyl is converted into bicyclohexyl. Depending upon the reaction condition~ it is possible to obtain benzene and any other dechlorinated products.
In this invention it is essential to emulsify and disperse PCB in an alkaline aqueous solution, thereby enabling the PCB to react with hydrogen effectively. The resulting hydrogen chloride reacts with the alkali content in the solution, thereby producing a harmless salt.
In this way the reaction smoothly proceeds. It has been found through experiments that a Raney nickel-catalyst preferably needs the parallel use of alkali for its lasting activity; otherwise the activity will not last. The alkali used for this invention can be selected from known ordinary types as long as they can react with hydrogen chloride to produce salts, such as sodium hydroxide, potassium hydroxidel calcium hydroxide, sodium carbonate. The amount of alkali to be used depends upon that of PCB to be treated, but it is necessary to use a ~ufficient amount to react with the whole amount of hydrogen chloride produced through the reaction of PCB with hydrogen. It is permissible to use a slightly excessive amount of alkali.
It has been also found that ~Then the alkali is one normal or less a better emulsifying and dispersing of PCB will be resulted, whereas when it is as highly concentraded as to exceed one normal the emulsifying and disper~ing thereof will decelerate, thereby resulting in a retarded reaction. In addition, it has been found that the reaction smoothly proceeds when the equivalent ratio to PCB ranges from 0.5 to 1.25, preferably from 0.7~ to 1.1 (especially in the range of 0.5 to 1.0 the reaction velocity is relatively high until it reaches the point of neutralization). Accordingly the amount of alkali is restricted by that of PCB to be treated, and it determines the minimum amount of a 10~-~580 dispersing medium. Furthermore, it has been found that the alkali and the reduction circumstances are effective to protect the reaction chamber, and that irrespective of the high concentration of alkali the Raney nickel catalyst main-tained its activity after the reaction was finished.
Preferably a suitable emulsifying-dispersing agent is used to emulsify and disperse PCB in an alkaline aqueous solution.
For this agent methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, and any other water soluble organic solvents, and surface active agents as long as they are effective to emulsify and disperse PCB in the alkaline aqueous solution are appropriately used. Its amount is not limited, but in the case of water soluble organic solvents, such as methyl alcohol, it is preferred that 20 to 50g is used against lOOg of water, wherein the exact figure depends upon the number of chlorides contained in the PCB to be treated. These agents can be used singly or in a combination.
In cracking PCB the ratio of water to the emulsifying-dispersing agent is 1.3 to 4:1, preferably 2:1 so as to secure the minimum amount of a dispersing medium. The amount of the emulsifying-dispersing agent affects the emulsifying and dispersing of PCB; neither excess nor shortage produces a good result. In making a solution containing a dispersed PCB it is also possible to use the same amount of emulsifying-dispersing agent as that of water, and in this case it has been found that methyl alcohol makes hydrogen most soluble of the three; then ethyl alcohol, and finally isopropyl alcohol.
The adding ratios of PCB, alkali an emulsifying-dispersing agent, and water are prefereably determined such 30 that the solution of 800 to 2000ml, preferably 900 to 1200ml, should contain alkali of 0.5 to 1.25 gram equivalent weight (preferably 0.75 to l.lgram e~uivaient weight) ~o~s~o ~:
.

and an emulsifying-dispersing agent of 100 to 450ml (preferably 170 to 380ml) with respect to chloride of l.Ogram contained in the PCB.
~ or the emulsifying-dispersing agents for use in this invention known types can be safely selected and used, e.g. Raney catalysts~, such as M Raney nickel catalyst, a Raney cobalt catalyst; modified Raney cataly~ts (which are produced by the addition of lead, antimony, etc. t~
a nicke~-aluminium alloy); platinum; palladium, and rhodium. These cataly~ts can be used singly or in a combination of two or more. The amount to be used depends upon the type of the catalyst and the reaction conditions, and can be determined in a wide range. For example, a 10%
~arbon-supported palladium catalyst of 1 to 3gram can be used with ~espect to lOOgram of PCB (AC 125~). It has been found that the Raney nickel catalyst is very reactive in the alkaline and neutral zones up~to - The desired pressures for carrying out this invention range from normal to lOOatm, preferably 3 to 30atm, and they are adjusted in accordance with the pressure of hydrogen. It is preferred to use a greater amount of hydrogen than that calculated on principle. The hydroge-native dechlorination reaction has been found to be almost free from the pressure, and therefore, its reaction velocity can be considered constant whether the initial pressure is lOOatm or 30atm. Even if the partial pressure of hydrogen is 1 to lOkgw~cm2, the reaction proceeds, and its velocity is comparable to when the pressure is high.
The method of this invention can be performed at a room temperature, but the higher the temperature is, the more the reaction accelerates.
However, w~en the temperature exceeds 200 C it may happen that the hydrogenation catalyst, such as a Raney catalyst, loses its activity, and it is preferred to carry out the reaction at a temperature of 50 to 200C, preferably 70 to loOC, particularly for an industrial 109~5130 ,. i ~ .

utilization. A period of time for which the reaction ccmpletes depends upon the activity of the catalyst, the reaction temperature and other factors, but normally it almost complete; in 0.5 to 48 hours.
The viscosity of PCB increases as the av~rage number of chlorides increases with a rising pour point, thereby making the qame difficult to become emulsified and dispersed in the solution. A 10-chloride compound has almost the same fluidity at 160 C as that of a 4-chloride compound at 100C, so that there is no difficulty for the same to become emulsified and dispersed, thereby enabling the reaction to proceed smoothly. In this case, it has been found that the elevation of the temperature makes the emulsifying and dispersing develop, and that the agitation of the solution also favorably affects the emulsifying and di~persing in keeping on as well as proceeding. In the case of a Raney nickel catalyst the practicable range of temperatures for the hydrogenation i~ up to 160 C in view of the effective continuation of activity. The reaction velocity tends to multiply 2 to 4 times in the range of 70 .~ to 200 C as the temperature rises by 10 C.
A typical example of the operation according to the present invention will be explained:
A hydrogenation catalyst, alkali, water and a dispersing agent are added in a high pressure container, such as an autoclave, in which a PCB is evenly emulsified and dispersed. ~hen hydrogen is introduced into the container, and the reaction is effected atthe required temperature under therequired pressure. After t~e reaction is finished, the products will be separated into each compound by fractional distil-lation at the utilization of differences in their boiling points, and be individually purified.
Alternatively, the following method is al~o possible:
Since the mixture in the container becomes ~radually separated 109~51~0 into products in the upper portion of the container and an u~reacted PCB in the lower portion thereof, in the course of the rcaction, the products in the upper portion are taken out while the reaction is being stopped, followed by a fresh supply of PCB to the remainder in the container. In this way the reaction resumes in the container, whereas the products obtained are separated into each compound by partial distillation.
As the th~rd alternative way it is also possible that the mixture in the contAiner is separated into an unreacted PCB and products by distillation in a closed system while the reaction is being stopped, in view of the remarkably high boiling point of PCB compared with those of the products. The products obtained in this way are separated into each compound by distillation.
A Brief Explanation of the Drawing:

FIGURE 1 is a graph depicting the relationship between the rate of dechlorination and the amount of an emulsifying-dispersing agent in a hydrogenation-dechlorination reaction of PCB having 4 -chlorid0s (reaction temperature: 100 C, reaction hour: 3hrs);
FIGURE 2 is a graph depicting the relationship among the amount of sodium hydroxide, the rate of dechlorination and a pressure drop (the emulsifying-dispersing agent: isopropyl alcohol, reaction temperature 100 C, reaction hour: 3hr~) The present invention will be better understood by the following examples:

9-0~ of PCB (made by Mitsubishi-Monsanto C-.Ltd. AC 1249, the average number of chlorides: 3), having 0.105gram equivalent weight, 4.2g of sodium hydroxide (0.105 gram equivalent weight)~ and 20ml of isopropyl alcoholwere niixed, to which lOg of powdered Ni-Al alloy ~ (Ni: 50%) was added as a catalyst together with water,:

~094S80 wherein the powdered Ni-Al alloy was previously develoI)ed at 50 C for 50 minutes with 45ml of 30% solution of sodium hydroxide,until the total amo~nt reached lOOml. This dispersing solution was added in an autoclave capable of osillation (with a Nickrome heater, capacity: 250m], and hydrogen was introduced. Then the reaction was effected at 100 C
under about lOOIcgw/cm of Hg total pressure,, wherein the vapor pha4e was 150ml. Table 1 shows the re:Lationshi,p amons the tot~l pressure of hydrogen in the autoclave, the rate of dechlorination and the reaction hour:

109~S~0 ~ ~
. ~ ~
.. _ _ _ _ . ... . . . .

REACTION HOUR PRESSURE 0~ Hg RATE OF DECHLORINATION( ) (hour) (kg / cm ~ ( 102.8 o,o 1 92.2 ~20.0)

2 88.o (llO.O)

3 85.o (50.5)

4 82.5 (70.5) 80.3 67.o .. (93.0) 24 62.8 g8.o (~) The rate of dechlorination was given by measuring the chloride produced in the form of sodium chloride by the sil~er chloride gravimetric method.

The parenthes:ized figures were obtained by experiments individually renewed for each stage.

It was ascertained through a gas chromatography and a gas chro-matography-mass spectrometry that the PCB had been converted into a great amount of biphenyl and a small amount of bicyclohexyl. In addition, it was ascertained by an ignition test on the filter paper that the catalyst maintained its activity after the reaction was finished.

The hydrogenation-dechlorination reaction was carried out in the same manner as Example 1, except for the reaction temperature, that is~ at 160 C. The relationship among the pres~ure of hydrogen in the autoclave, the rate of dechlorination and the reaction hour are ~hown in Tabl e 2:

109~580 TA~LE 2 REACTION HOURPRESSURE 0~ Hg RATE OF DECHLORINATION
(minute~ (kg / cm ) . . (%) 0 100.0 0.0 92.5 (38.o) 3 85.o (78.o) 65.5 (85.o) 120 . 67.o . 97.5 It was ascertained by an ignition test on the filter paper that the catalyst maintained it~ activity after the reaction was fini~hed.

The hydrogenation-dechlorination reaction was carried out in the same manner as Example 1, except for the reaction temperature, that is, at 200 C. The relationship among the pressure of hydrogen in the autoclave, the rate of dechlorination and the reaction hour are shown in Table 3:

REACTION HOURPRESSURE 0~ Hg RATE OF DECHLORINATION
(minute) (kg / cm ) (%) 0 100.0 0.0 ~2.0 ' 50.0 80.2 82.5 ~0 60.0 91.5 It was aqcertained by An ignition test on the filter paper that the catalyst maintained its activity after the reaction was finished.

In~tead of the isopropyl alcollol in EXAMPLE 1 20ml of m~thyl 10~'1S80 ~ !
~ . - . I , . . .
. .

alcohol was used to carry out the hydrogenation-dechlorination reaction. The relationship between the pressure of hydrogen in the autoclave and the reaction hour is shown in Table 4:

REACTION HOUR PRESSURE 0~ Hg (hour) ( kg / cm 0 133.5 1 124.5 2 114.5 3 107.0 4 97.5 6 90.0 24 89.0 After 24 hours it was found that the rate of dechlorination reached 87%, and it was a~certained by an ignition test on the filter paper that the catalyst maintained its activity after the reaction was finished.

The hydrogenation-dechlorination reaction was carried out in the same manner as Example 1, except for 20ml of acetone for the catalyst and under a 70kgw/cm total preqsure of hygrogen. The reaction was continued for 20 hours, and the relationship amonS the reaction hour, the pressure of hygrogen and the rate o dechlorination is shown in Table 5:

(Table 5 is on the next page) :1.0 -~

~ 10!~580 . . ~ i _ . .
:`

Reaction temperature: 100C

REACTION HOURPRESSURE 0~ Hg RATE OF DECHLORINATION
(hour) (kg / cm ) (%) 70.5 0.0 0.25 51.5 o.5 38.1 1.0 34.0 1.5 31.2 2.0 27.2 18.0 2.5 19 . 2~4 2~4 100.0 After the reaction the Raney nickel catalyst was found in black and sludgy, and it was ascertained by an ignition test on the filter paper that the catalyst had no more activity. It was also found thro~gh a gas chromatography and a gas chromatography-masq spectrometry that the PCB had been converted into biphenyl and bicyclohexyl, and that the acetone had been converted into isopropyl alcohol.

Instead of the acetone in Example 5 20ml of ethyl alcohol was used to carry out the hydrogenation-dechlorination reaction. The relationship among the reaction hour, the pressllre of hydrogen and .
the rate of dechlorination is shown in Table 6:

Reaction temperature: 100C

REACTION HOUR PRESSURE 0~ Hg Rate OE DECHLORINATION
(hour) ~kg / cm ) (%) 72.0 .0 109'~30 `' '' I

0.5 69.6 1 67.7 1.5 67.o 2.0 66.2 18 45.5 19 45.4 44.4 - 92.0 After the reaction was finished, it was ascertained by an ignition test on the filter paper that the Raney nickel catalyst maintained its activity, and it was also ascertained through a gas chromatography and a gas chromatography-mass spectrometry that a great amount of biphenyl and a small amount of bicyclohexyl had been produced.

The hydrogenation dechlorination reaction was carried out, using a PCB having 3 chlorides on an average, under 30kgw/cm total pressure of hydrogen but at various temperatures, that is, 100 C, 160 C and 200 C. The relationship among the reaction hour, the pressure of hydrogen and the rate of dechlorination is shown in Tables 7, 8 and 9.
o Herein the page 12' is inserted.

Reaction temperature: 100C

REACTION HOURPRESSURE OE2Hg RATE OF DECHLORINATION
(hour)~kg / cm ) (%) 32.0 o. O
1 25.5 (31.') 2 22.5 (53.~)) 3 1~.0 (50.6) .5.2 (80.3) ll.o

5~30 ,..., B In an autoclave 9g of PCB (AC 1242~, 20ml of isopropyl alcohol,and 4.2g of sodium hydroxide were mixed, to which 10g of a Raney nickel alloy powder (Ni: 40%) and about 74ml of water were added until the whole liquid phase containing the catalyst reached 100ml.
The Raney nickel alloy powder had been previously developed at 60 C
for 50 minutes in a 55ml of 20% sodium hydroxide solution.
It was found that at the temperatures of 160 and 200 C the partial pressures of the dispersing agent (isopropyl alcohol) and water rose, and 150ml of hydrogen was introduced into the autoclave such that the total pressure at each temperature could maintain 3Okg/cm .

- 12 ~ -10~A1S80 :`

6 7.2 (~3.7) 18hour/25min 4.0 96.1 Reaction temperature: 160C

REACTION HOUR PRESSURE O~ Hg RATE OF` DECHLORINATION
(minute) (kg / cm ) (~) 26.4 0.0 22.0 20.5 19.0 17.0 15.0 61.2 Reaction temperature: 200C

REACTION HOUR PRESSURE O~ Hg RATE OF DECHLORINATION
(minute) (kg / cm ) (%) 52-5 0.0 40.5 5~-3 After the reaction was finished, it was found that the Raney nichel catalyst in the reaction at 100 C maintained such an activity that it ignited as vigourously as before the reaction, when the same was cleansed with ethyl alcohol, and that the catalyst in the reaction at 160 C ignited when the same was cleansed~with acetone.
On the other hand, the catalyst in the reaction at 200 C did not ignite even wllen the same was c]eansed ei-thcr with ethyl ulcollol or acetone.
It was ascertained through a gas chromatosraphy and a gas chromato-sraphy-mass spectrometry tha-t a sreat amount o~ ~-iphenyl and a small - 1,3 ~

~0!~4580 . ') .,' .

~ , ., . . , _~
.

amount of bicyclohexyl had been produced.

This experiment was effected with the use of a PCB having 4 chlorides on an average, at 100C under a 30kg~cm to-tal pressure of hydrogen, the results of which are shown in ~ ble 10. 7.65g of PCB
~ 09~f ~o~
t (produced by Kanegafuchi Kagaku Co., Ltd. KC-400~) having 0.105 gram equivalent weight, 20ml of isopropyl alcohol, and 4.2g of sodiumhydroxide (equivalent weight ratio to the PCB: 1) were mixed in an autoclave, to which lOg of a Raney nickel alloy powd~r (Ni: 40%) wa~ added together with water (about 63ml) until the whole amount of the solution reached lOOml, wherein the Raney nickel alloy powder wae previously developed at 60 C for 50 minutes in 55ml of 20% solution of sodium hydroxide.
into the autoclave Then hydrogen was introduced~sufficiently to secure that the total pressure thereof reached 30kg/cm .

Reaction temperature: 100C

REACTION HOURTOTAL PRESST2RE OF Hg RATE OF DECLORINATION
~hour)(kg / cm ) (%) 0 31.2 O.Q
0.5 25.2 1 21.2 1.5 17~IL
2 1ll.0 2.5 11.3 3 8.2 98-5 Twenty-four hours after the reaction was finished, it was found by a~ ~gnition test that the Raney nickel catalyst showed the same igniting ability as before the reaction, which demonstrated that it maintained its catalytic activity. In addition, it was ascertained through a gas chromatography and a gas chromatography-mass specrometry that a great amount of biphenyl and a small amount of bicyclohexyl had ~- 10~580 .~

been produced~
Comparative Test ~1) The reaction was carried out in the same manner as Example 8, except for non-use of alkali. The relationship among the reaction hour, the total pressure of hydrogen and the rate of dechlorination is shown in Table 11:

REACTION HOUR TOTAL PRESSU ~ OF Hg RATE OF DECHLORINATION
(hour)(kg / cm ) (%) 0 34.2 0.0 0.5 34-3 1.5 33.3 2.5 32-7 3 32.6 15.0 it was found that After the reaction was finished~thepH had changed into about 5.5.
The catalyst was found in black and sludgy, and an ignition test did not show that the catalyst maintained its activity , which showc that without alkali the catalytic activity does not last, thereby resulted in a short life of reaction.
Comparative Test (2) A hydrogenation-dechlorination reaction was effected in the same manner a~ Example 8, except for non-use of the emulsifying-dispersing agent. The relationship among the reaction hour, the total pressure of hydrogen, and the rate of deehlorination is shown in Table 12:

5~qO
'` .

REACTION HOUR TOTAL PRESSU~E OF Hg RATE OF DECHLORINATION
(hour) (kS / cm ) (%) 0 31.3 0.0 0.5 32.1 1 32.1 1.5 32.1 2 32.1 2.5 32.1 3 32.1 1.26 No pressure drop was recognized, but it was found by an ignition test that the catalyst maintained its activity after the rection was finshed. This test shows that without the use of an emulsifying-dispersing agent a dispersion required for effecting the reaction cannot be developed as long as the temperature remains 100C or around.

The hydrogenation-dechlorination reaction was effected in the same manner as Example 8, except for the use of a PCB having 5 chlor~des,~
.0 ~ ~/~r ~r on an average. 6.80g ~0.105 gram equivalent weight) of the PCB (KC-500~) was used. The results are shown in Table 13:

Reaction temperature: 100C

REACTION HOUR TOTAL PRESSU~E OF Hg RATE OF DECHLORINATION
(hour) (kg / cm ) (%) 0 30.9 0.0 0.5 ' 26.0 2?~2 1.5 20.0 2 18.0 2.5 16.0 3 15.3 83.7 _ 16 10'3'~ 0 ; , .. . . , . . . . . . . .. _ Twenty-four hours after the reaction was finished, an ignition test was conducted upon the Raney nickel catalyYt, and it was found that it ignited in the same manner as before the reaction, which shows that its catalytic activity was maintained after the reaction.In addition, it was ascertained through a gas chromatography and a gas chromatography-mas~ spectrometry that a great amount of biphenyl and a small amount of bicyclohexyl had been produced.

The hydrogenation-dechlorination reaction was effected in the same manner as Example 8, except for the use of a PCB having 6 chlorides on an average. 6.29g (0.105 gra~ equivalent weight) of the PCB was used.
The results are shown in Table 14:

TABLE l4 Reaction temperature: 100C

REACTION HOURTOTAL PRESSU ~ OF Hg RATE OF DECHLORINATION
(hour)(kg / cln ) (%) 0 31.4 0.0 -5 31.0 1 27.3 1.5 25.0 2 22.5 2.5 20.2 3 17.9 74-~15 Twenty-four hours after the reaction was finshed, it was found by an ignition test that the catalyst maintained its activity, and additionally it was ascertained through a chromatography and a gas chromatography-mass spectrometry that a great amount of biphenyl and a small amount of bicyclohexyl had been produced.
EXAMPLE ll The hydrogenation-dechlorination reactions were effected, u~ing 103`~S~0 .
' a PCB having 10 chlorides on an average, at 160 C, (1) with 40ml of isopropyl alcohol and (2) with 30ml thereof for a dispersing agent.
The results of these two reactions are shown in Tables 15 and 16, respectively. The other conditions were the same as Example 8. But under the use of 30ml of the agent the reaction was continued for 4 hours.

Reaction temperature: 160C Dispersing agent: 40ml Reaction hour: 3hr REACTIQN HOUR TOTAL PRESSU ~ OF Hg RATE OF DECHLORINATION
(hour)(kg / cm ) (%~
28.5 0.0 -5 26.9 1 23.7 1.5 21.2 2 Ig.9 2.5 18.9 3 18.7 82. 6fi After the reaction was finished, it was found that the Raney nichel catalyst had been reduced in size to grains of 1 to 3mm, and after the same was cleansed with ethyl alcohol, an ignition test showed that it maintained its catalytic acti~ity though it slightly lowered. It has also beenascertained through a gas chromatography and a gas chromatography-mass spectrometry that a great amount of biphenyl and a small amount of bicyclohexyl had been produced.

Reaction temperature: 160C Dispersing agent: 30ml Reaction hour: 4hr REACTION HOUR TOTAL PRESSU~E OF llg RATE OE DECHLORINATION
(hour)(kg / cm ) (~/o) 33.8 0.0 0.5 28.9 - lo 1()~?~580 . . ~

1 26.1 1.5 23.0 2 21.3 2.5 21.0 3 21.0 3~5 20.9 4 20.9 91.86 After the reaction was finished, it was found that the catalyst had been also reduced in size to grains, but that its catalytic activity remained though it slightly lowered, which was ascertained by an ignition test. It was also found through a gas chromatography and a gas chromatography-mass spectrometry that a great amount of biphenyl and a small amount of bicyclohexyl had been produced.

Instead of the Raney nickel catalyst in Example 8 250mg of carbon-supported palladium catalyst (10%) was used to effect the hydrogenation-dechlorination reaction, in which the reaction was continued for 2 hours and a half. The results are shown in TABLE 17:

Reaction temperature: 100C

REACTION HOUR TOTAL PRESSU~E OF Hg RATE OF DECHLORINATION
(hour) (kg / Cm ) (% ) 3-5 0.0 0.25 12.9 0.5 11.2 1.0 9.6 1.5 8.2 2.0 7.2 2.5 6.~ 100.0 It was ascertained through a gas chromatosraphy and a gas _ ~9 5~0 chromatography-mass spectrometry that the PCl3 had been c)nverted into a great amount of biphenyl and a small amount of bicyclohexyl.
.

7.65g of PCB (KC-400) having 4 chlorides on an averase (0.105 gram equivalent weight), 6.18g of potassium hydroxide (0.105~ram equivalent weight), and 30ml of ethyl alcohol for a dispersing agent were mixed, and the hydrogenat~on-dechlorination reaction was effected under a 30kgw/cm total pressure of hydrogen and with lOOmg of a carbon-supported palladium catalyst (10%~. The reaction was carried out at 100C for 2 hours and a half, the results of which are shown in Table 18;

REACTION HOUR TOTAL PRESSUR~ OF HS RATE OF DECHLORINATION
(hour)(kg / cm ) (%) 0 29.9 0.0 0.2525.3 0.520.1 1 16.9 1.516.4 2 16.1 2.5 15-9 86.o It wa~ found through a gas chromatography and a gas chromatograph-mass specrometry that the products contaihed a great amount of biphenyl and a small amount of bicyclohexyl.

The hydrogenation-dechlorinQtion reaction was effected in the same manner as Example 8, except for the use of 500mg of 5~0 platinum car~on, the result~ of which are shown in Table 19:

~() _ iO~9~S80 _ . . . , ,, . _ TA~LE 19 REACTION HOUR TOTAL PRESST2RE OE llg RATE OF DECHLORINATION
(hour) (kS / cm ) (%) o 32.8 0.0 0.5 31.9 1 30.o 1.5 3~-2 29.1 2.5 28.2 3 27.2 25.4 It was found through a gas chromatography and a gas chromatography-mass spectrometry that the products contained a great amount of biphenyl and a small amount of bicyclohexyl.

This experiment is a modification to Example 8 in which the m~xing ratio of isopropyl alcohol and water was changed. The results are depicted by the graph in FIGURE 1. It was found that with the use of lOml of isopropyl alcohol the decomposition rate was not sufficient irrespective of the remaining catalytic activity. Even in the case of a PCB having 3 chlorides the decomposition rate did not remarkably im-3 hour prove during the~reaction.When the dispersing agent is added more than water (exceeding 50ml), the decomposition rate becomes worse, and when it amounts to 70ml, an alkaline decomposition only occurs, in which the PCB will be found slightly in brown.

In this experiment the amount of sodium hydroxide in Example 8 was variously changed, the results of which are depicted by the graph in FIGURE 2.
The graph shows that the decomposition rnte fnlling in the range of 0.75 to 1.25 equivalent weisht ratio to PCB is bctter thnn in other ranges. Under the conditions of Example ~, Whell the ratio ~0~580 ;

.

of sodium hydroxide equivalent weight to PCB is not grsater than 1, the rate of dechlorination is almost equal to the ratio of equivalent weight, from which it is understood that the reaction accelerateS in the zone ranging from the point of neutralization to the acid zone.
In this case, after the reaction is finished, the catalyst loses its activity.
When the ratio is greater than 1, the rate of dechlorination becomes equally worse; when it is up to 1.25 or around the rate of dechlorination still exceeds 50%, but when the ratio is greater than 1.25, it adversely affects the decomposition. The catalytic activity is maintained when the ratio of sodium hydroxide equivalent weight to PCB ranges from 1 to 2.
In a mixture of water and isopropyl alcohol (mixing ratio: about 2 to 1) the optimum concentration of sodium hydroxide is lN, and it is understood that it is closely connected with the fact that when the concentration of alkali is less than lN, a good dispersion is resulted.

Claims (15)

WHAT WE CLAIM IS:

1. A method of disposing of PCB polychlorinated biphenyls which comprises emulsifying and dispersing the PCB to be treated in an alkaline aqueous solution, and reacting said PCB with hydrogen in the presence of a hydrogenation catalyst.

2. A method of disposing of PCB which comprises emulsifying and dispersing the PCB to be treated in a solution containing alkali and an emulsifying-dispersing agent, and reacting said PCB with hydrogen in the presence of a hydrogenation catalyst.

3. A method as claimed in Claim 2 in which the amount of said solution is between 800ml and 2000ml containing alkali of 0.5 to 1.25 gram equivalent weight and an emulsifying-dispersing agent of 100 to 450ml with respect to chlorine of 1.0 gram equivalent weight contained in said PCB.

4. A method as claimed in Claim 2 in which the amount of said solution is between 900ml and 1200ml containing alkali of 0.75 to 1.1 gram equivalent weight and an emulsifying-dispersing agent of 170 to 380ml with respect to chlorine of 1.0gram equivalent weight contained in said PCB.

5. A method as claimed in Claim 3 in which said treatment of PCB is performed at a temperature of 50 to 200°C under a pressure of normal to 100atm.

6. A method as claimed in Claim 3 in which said treatment of PCB is performed at a temperature of 70 to 160 C under a pressure of 3 to 30atm.

7. A method as claimed in Claim 3 in which said alkali is sodium hydroxide.

8. A method as claimed in Claim 3 in which said alkali is potassium hydroxide.

9. A method as claimed in Claim 3 in which said emulsifying-dispersing agent is methyl alcohol.

10. A method as claimed in Claim 3 in which said emulsifying-dispersing agent is ethyl alcohol.

11. A method as claimed in Claim 3 in which said emulsifying-dispersing agent is isopropyl alcohol.

12. A method as claimed in Claim 3 in which said emulsifying-dispersing agent is acetone.

13. A method as claimed in Claim 3 in which said hydrogenation catalyst is a Raney nickel catalyst.

14. A method as claimed in Claim 3 in which said hydrogenation catalyst is a carbon-supported palladium catalyst.

15. A method as claimed in Claim 3 in which said hydrogenation catalyst is a platinum catalyst.