WO1996009092A1

WO1996009092A1 - A method for decomposing halogenated organic compounds

Info

Publication number: WO1996009092A1
Application number: PCT/AU1995/000595
Authority: WO
Inventors: Roger Philip Smart
Original assignee: Adi Limited
Priority date: 1994-09-20
Filing date: 1995-09-12
Publication date: 1996-03-28
Also published as: AUPM826294A0

Abstract

A method for decomposing halogenated organic compounds, particularly polychlorinated biphenyls, is disclosed. The method comprises the steps of: (a) forming a reaction mixture comprising: (i) halogenated organic compounds; (ii) an alkali hydroxide; (iii) an organic solvent; (iv) an aliphatic alcohol; and (b) heating the reaction mixture at a temperature and for a time that is sufficient to decompose the halogenated organic compounds.

Description

A METHOD FOR DECOMPOSING HALOGENATED ORGANIC COMPOUNDS

The present invention relates to a method for decomposing halogenated organic compounds.

In particular, the present invention relates to a method for decomposing polychlorinated biphenyls (PCBs) .

There are a wide range of known commercial applications for PCBs due to the ability of PCBs to withstand high temperatures without degradation. By way of example, the commercial applications include the use of PCBs in products such as paints, inks, plastics, "carbonless paper", electrical equipment, heat exchangers, and hydraulic systems. However, the use of PCBs has rapidly declined recently as studies have shown that PCBs have adverse toxicological and ecological effects.

The high stability of PCBs, which was once seen to be a positive property has now presented problems in the development of suitable methods for the disposal of PCBs.

One known method of disposal of halogenated organic compounds in general and PCBs in particular is the destruction of PCBs by incineration. However, incineration is prohibited in Australia, and the cost of shipping PCB- contaminated material to countries in which incineration is permitted is extremely high.

Other known methods of disposal of halogenated organic compounds in general and PCBs in particular are based on chemical decomposition of PCBs.

One such method disclosed in U.S. patents

4,417,977 and 4,602,994 of Pytlewski et al involves the reaction of halogenated organic compounds with a reagent known as "NaPEG" . This reagent may be formed by one of several methods. One such method involves the reaction of metallic sodium with polyethylene glycol under nitrogen.

A similar method disclosed in U.S. patent 4,460,797 of Pytlewski et al involves the reaction of halogenated organic compounds with a reagent known as "NaOH-PEG". Approximately equal parts of sodium hydroxide and polyethylene glycol are used to form this reagent. This reagent may be formed prior to the dehalogenation reaction, or alternatively in situ.

Usually, one mole of the NaPeg or NaOH-PEG reagent is used in the reaction per mole of halogen in the halogenated organic compound. The reagent, or the materials used to form the reagent in situ, is/are mixed with a contaminated material and the mixture is heated to temperatures up to 220°C. The contaminated material may be a solution of halogenated compounds in an organic solvent such as oils.

These methods for the decomposition of halogenated organic compounds are inadequate for use in a commercial plant for a range of reasons including the time required to achieve a high enough degree of dehalogenation and the inability of the methods to dehalogenate highly concentrated mixtures of halogenated organic compounds.

An alternative method for decomposing halogenated organic compounds, such as PCBs, is disclosed in U.S. patent 5,019,175 of Rogers et al. In accordance with the method, an aqueous solution of polyethylene glycol is added to a mixture containing the halogenated organic compounds and an alkali metal hydroxide. The mixture is heated to remove the water and thereafter is heated further to effect destruction of the halogenated organic compounds. It has been found by the applicant that this method is difficult to commence, and once the reaction has been commenced, takes considerable time to reach completion.

U.S. patent 5,064,526 of Rogers et al discloses an improvement to the method disclosed in Rogers U.S. patent 5,019,175. The improved method is based on the addition of a hydrogen donor compound and a catalytic source of carbon to a reaction mixture of a contaminated material and an alkali or alkaline earth metal carbonate, bicarbonate or hydroxide. The reaction mixture is heated to remove the water and thereafter is heated further at a temperature of between 200 and 400°C. After completion of the reaction an acid is added in an amount sufficient to neutralise the mixture. This method is unsatisfactory because an excessive time is required to reduce the level of halogenated organic compounds to a sufficiently low level. This is particularly so where the contaminated material contains very high concentrations of halogenated organic compounds, for example up to 300,000 parts per million (ppm) . n fact, it has been found by the applicant that once the concentration of halogenated organic compounds exceeds 20,000 ppm, the time taken to complete the reaction is highly dependent on the hydrogen donor compound.

Whilst it is reported by Rogers et al that hydrogen donor compounds include organic compounds such as high boiling point solvents, fatty acids, aliphatic alcohols or hydrocarbons and the like, very few known hydrogen donor compounds have a high enough hydrogen donor capacity to allow for the practical treatment of mixtures with a halogenated organic compound concentration of above 10%.

Even with the very best fuel oils as hydrogen donors this reaction tends to have a very long tail, which appears to result from the diminishing hydrogen donor capacity of the oil during reaction.

Additionally, the applicant has found that materials with a high hydrogen donor content are not widely available. At present, the applicant has found only two oil sources which contain a sufficiently high hydrogen donor content to react with high concentrations of halogenated organic compounds (300,000 ppm). The hydrogen donor content of all other oil sources tested by the applicant depleted rapidly in the reaction mixture, thus leading to increased reaction times and decreased halogenated organic compound destruction.

An object of the present invention is to provide a method for decomposing halogenated organic compounds which alleviates the disadvantages of the known methods described above.

According to the present invention there is provided a method for decomposing halogenated organic compounds comprising:

(a) forming a reaction mixture comprising:

(i) halogenated organic compounds;

(ii) an alkali hydroxide;

(iii) an organic solvent;

(iv) an aliphatic alcohol; and

(b) heating the reaction mixture at a temperature and for a time that is sufficient to decompose the halogenated organic compounds.

It has been found by the applicant in laboratory experimental work that the above-described method can substantially decompose halogenated organic compounds such as PCBs.

It is believed by the applicant, on the basis of laboratory experimental work, that the above-described method can be operated under temperature and reaction time conditions which will provide the basis of a commercial plant for decomposing halogenated organic compounds.

Whilst the applicant does not wish to be bound by a particular theory at this point, the applicant believes that substantial decomposition of halogenated organic compounds that can be achieved with the present invention is a consequence of the aliphatic alcohol making the alkali hydroxide at least partially soluble in the organic solvent and thereby forming an essentially homogeneous reaction mixture which provides improved opportunities for decomposition to take place.

In the circumstances, it is believed by the applicant that the amount of the aliphatic alcohol should be selected to be sufficient to improve the solubility of the alkali hydroxide in the organic solvent.

It is preferred that temperature of heating step (b) be greater than the melting point of the alkali hydroxide.

It is preferred particularly that the temperature be greater than 200°C.

It is preferred more particularly that the temperature be greater than 250°C.

Typically, it is preferred that the temperature be greater than 300°C.

It is preferred that the organic solvent have a boiling point greater than the temperature of heating step (b) .

It is preferred particularly that the organic solvent be a hydrocarbon oil.

It is preferred that the halogenated organic compounds be PCBs. It is noted that the present invention is not limited to the decomposition of PCBs and may extend to other halogenated organic compounds such as halogenated pesticides.

It is preferred that the alkali hydroxide be selected from the group comprising sodium hydroxide, potassium hydroxide, and lithium hydroxide, or mixtures thereof. It is preferred that the aliphatic alcohol have a non- polar hydrocarbon tail.

It is preferred that the aliphatic alcohol have at least 9 carbon atoms.

It is preferred that the aliphatic alcohol have no more than 22 carbon atoms.

It is preferred particularly that the aliphatic alcohol be an unbranched aliphatic alcohol.

It is preferred more particularly that the aliphatic alcohol have only one OH functional group.

It has been found by the applicant that commercial grade aliphatic alcohols with carbon chain lengths of between 16 and 18 carbon atoms have boiling points that are greater than 300°C, typically greater than 320°C, are inexpensive and are relatively stable under the reaction conditions of the present invention as described above.

It is preferred that the method further comprises extracting the halogenated organic compounds from a contaminated material prior to steps (a) and (b) above.

The extraction of the halogenated organic compounds may be achieved, by way of example, by heating the contaminated material at a temperature that is sufficient to evaporate the halogenated organic compounds and thereafter collecting the condensed vapour.

At completion of the reaction, the hydrocarbon oil free from halogenated organic compounds may be recovered for recycling into further reactions or used as a fuel oil supplement by means of vacuum distillation or hot ultrafiltration, leaving a solid cake of carbon, sodium chloride and sodium hydroxide for further processing or disposal .

The method of the present invention is suitable for use on reaction mixtures having a wide range of concentrations of halogenated organic compounds. By way of particular example, the method is suitable for use on reaction mixtures of 20-30% halogenated organic compounds, which is a commercially viable target for PCB decomposition. Unless otherwise stated, all references to a percentage amount are to be construed as references to percent by weight.

The method may be performed on a batch or a continuous basis.

The order of mixing the reagents (ii), (iii) and (iv) with the halogenated organic compound is not a critical factor affecting the success of the decomposition reaction.

The present invention is described further with reference to the following examples.

The order of addition of reagents in the examples is merely illustrative of the typical order in which the reagents are added.

In the examples, unless otherwise stated, the following experimental method was employed. The organic solvent was placed in a stirred reaction vessel fitted with a reflux condenser and a Dean & Stark moisture receiver. The halogenated organic compound, such as pure PCB, was added to the solvent, followed by the alkali hydroxide and the aliphatic alcohol. As a purely precautionary measure, the sealed vessel was flushed with a nitrogen gas to remove any oxygen.

The reaction mixture was agitated and heated to approximately 270°C - 320°C to initiate reaction. The temperature was maintained at 270°C - 320°C until the initial rapid reaction subsided and was then increased to 350° for 1 to 2 hours to complete the reaction.

Where the examples involve the decomposition of a mixture containing greater than 10% highly chlorinated organic compounds, the above-described general experimental method was altered by gradually adding the chlorinated organic compound to a stirred preheated mixture of the organic solvent, alkali hydroxide and aliphatic alcohol. The mixture was then preheated to 320°-350°C and the chlorinated organic compound was added at such a rate as to maintain a steady reaction rate as evidenced by the rate of water distillation.

In the examples described as 'batch addition' experiments, the chlorinated organic compound was added sequentially in batches at temperatures about 10 to 20°C below the determined temperature of reaction initiation. The temperature was then raised until a rapid initial reaction commenced. The reaction mixture was then cooled to the previous addition temperature for addition of the next batch of organo chlorine. When all of the chlorinated organic compound had been added the reaction was continued to completion for 1 - 2 hours at about 350°C.

in the examples, unless otherwise stated, the hydrocarbon oil used was a purified paraffinic hydrocarbon oil Sunpar LW107 obtained from Sunoco Pty Ltd (Philadelphia USA) . Example 1

In this example, a range of aliphatic alcohols was investigated for their suitability for use in the method of the invention.

In each experiment, 50 grams sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of an aliphatic alcohol. To this mixture, 50 grams PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis for each experiment are presented in Table 1 below.

Table 1

Alcohol C5 C8 CIO C16 C22 C16-C18

Time % PCB destruction (minutes)

30 10.7 26.7 71.8 70.5 71.7 69.7

60 14.5 38.0 87.4 85.8 86.7 83.0

90 19.4 46.6 91.2 90.4 90.0 89.7

120 95.1 93.6 92.5 91.9

150 97.0 97.4 97.5 96.2

180 99.9 99.9 99.9 99.9

In Table 1, C5 refers to 1-pentanol, C8 to 1-octanol, CIO to 1-decanol, C16 to 1-hexadecanol, C22 to docosanol, and C16-C18 to commercial grade aliphatic alcohols including:

Hydrenol MY (Malaysia) Rofanol P80/85 (Indonesia) Rofanol P50/55 (Indonesia)

Salim C16/18 (70/30) (Indonesia) Salim C16/18 (30/70) (Indonesia)

The tabulated results illustrate that aliphatic alcohols having at least 9 carbon atoms are suitable for use in the method of the invention. The experimental procedure was repeated using 1,2 tetradecane diol, 1,2 hexadecane diol, oleyl alcohol, 1,10 decane diol, and 1,12 dodecane diol. The applicant found that the first 3 aliphatic alcohols produced significantly better results, in terms of decomposition of PCBs, than the last 2 aliphatic alcohols. It is believed by the applicant that the significantly better results may be linked to the fact that the first 3 aliphatic alcohols have non-polar hydrocarbon tails.

Example 2

In this example the concentration of aliphatic alcohol in the reaction mixture was varied to establish whether the concentration of aliphatic alcohol places any limit on the decomposition reaction.

50 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and from 2 to 20 grams C16-C18 aliphatic alcohol. To this mixture, 50 grams of PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis are presented in Table 2 below.

Table 2

Alcohol 2 5 10 20 (grams)

Time % PCB destruction (minutes)

30 34.2 69.7 81.2 86.4

60 49.3 83.0 91.0 90.4

90 56.2 89.7 93.7 92.8

120 65.7 91.9 95.5 95.2

150 79.4 96.2 98.2 96.7 180 84.9 >99.9 >99.9 >99.9

210 91.8

240 >99.9

The tabulated results indicate that varying the concentration of aliphatic alcohol (above a concentration sufficient to increase the solubility of the alkali hydroxide) does not significantly affect the efficiency of the method of decomposition.

Example 3

In this example, the effect on decomposition of variations in the concentration of halogenated organic compound was investigated.

From 20 grams to 195 grams of sodium hydroxide (1.8 mole/mole chlorine) was added to a mixture of 450g hydrocarbon oil and 5 grams of C16-C18 aliphatic alcohol. To this mixture, from 20 grams to 195 grams of PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis are presented in Table 3 below.

Table 3

PCB (grams) 20 50 113 193 NaOH (grams) 20 50 115 195

Time % PCB destruction (minutes)

30 43.4 13.5 20.7 29.6

60 80.4 79.7 46.2 45.5

90 86.9 86.4 84.6 56.7 120 95.6 90.7 90.1 70.0

150 >99.9 96.6 96.1 78.9

180 >99.9 99.2 85.5

210 >99.9 90.2

240 93.3

270 96.7

300 >99.9

The results illustrate that the method of the invention is suitable for use on reaction mixtures having a wide range of concentrations of halogenated organic compounds.

Example 4

In this example, a variety of organic solvents were tested for suitability in the method of the invention. The organic solvents tested included hydrocarbon oils having a high hydrogen donor capacity (oil 3) and hydrocarbon oils having a low hydrogen donor capacity (oils 1, 2, 4 and 5) .

50 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of C16-C18 aliphatic alcohol. To this mixture, 50 grams of PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis are presented in Table 4 below.

Table 4

Oil 1 2 3 4 5

Time % PCB destruction (minutes) 30 69.7 65.3 72.3 57.1 67.8

60 83.0 80.1 84.2 83.6 81.3

90 89.7 88.6 89.5 89.8 90.5

120 91.9 91.7 93.3 93.0 93.1

150 96.2 96.9 98.6 97.9 97.4

180 >99.9 >99.9 >99.9 >99.9 >99.9

Oil 1 = Sunpar (Sunoco USA) LW107 paraffinic oil

Oil 2 = BP WM6 medicinal white paraffin oil

Oil 3 = Shell Marine Fuel Oil 25

Oil 4 = Shell Electrical Transformer oil

Oil 5 = BP Machinery Oil CS68

Near identical results were obtained for all hydrocarbon oils tested. Therefore, this example illustrates that the method of the invention is not dependent on the hydrogen donor capacity of the oil and that a large range of organic solvents having a high boiling point are suitable for use in the method of the invention.

Other organic solvents tested and found to be suitable include laboratory grade paraffin (white) oils from Fisons & Sigma Aldrich, BP Machinery oils ranging in viscosities from 22 to 320 cS and crude and in- process oils from a Shell lubricating oil refinery.

Example 5

In this example the effect on decomposition of a range of alkali hydroxides was investigated.

50 grams of alkali hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of C16-C18 aliphatic alcohol. To this mixture, 50 grams of PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis are presented in Table 5 below.

Table 5

Alkali 1 2 3 4

Time % PCB destruction (minutes)

30 69.7 81.6 78.5 74.4

60 83.0 88.0 82.1 82.7

90 89.7 93.5 93.7 91.2

120 91.9 96.7 96.5 92.3

150 96.2 98.8 98.6 97.0

180 >99.9 >99.9 >99.9 >99.9

Alkali 1 NaOH Alkali 2 ROH (Note that the initial reaction when using KOH is frequently very vigorous)

Alkali 3 NaOH:KOH 1:1 Alkali 4 NaOH:KOH 4:1

Accurate comparative data for lithium hydroxide is limited due to the difficulty in preparing this alkali in an anhydrous state equivalent to sodium or potassium hydroxides. However small trial reactions indicate that the reactivity is LiOH > KOH > NaOH.

Example 6

In this example, the effect on decomposition of varying the concentration of alkali hydroxide was investigated.

Between 25 grams and 75 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of C16-C18 aliphatic alcohol. To this mixture, 50 grams of PCB (48% chlorine) was added. The reaction mixture was agitated vigorously and the temperature raised to 320°C for 120 minutes, then to 350°C for 60 minutes. The degree of PCB destruction was tested at regular intervals and the results of the analysis are presented in Table 6 below.

Table 6

Alkali 25 35 50 65 75 (grams)

Time % PCB destruction (minutes)

30 43.8 61.4 69.7 74.3 86.9

60 52.0 66.7 83.0 89.6 89.6

90 56.2 68.7 89.7 93.5 96.5

120 58.3 69.8 91.9 96.1 98.1

150 60.4 70.8 96.2 >99.9 >99.9

180 67.7 75.0 >99.9

210 72.9 79.1

240 75.0 83.3

It can be seen from the tabulated results that where the amount of alkali hydroxide used is less than 1.8 times the amount of chlorine in the halogenated organic compound, complete decomposition of the halogenated organic compound is not achieved in a practical time. In addition, it can be seen that the addition of an excess of alkali hydroxide does not significantly improve the decomposition results.

Example 7

In this example the effect on decomposition of varying the reaction temperature was investigated.

120 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of C16-C18 aliphatic alcohol. To this mixture, 80 grams crude hexachlorobenzene (HCB) was added. The reaction mixture was agitated vigorously and the temperature raised to the temperatures indicated in Table 7.

After 180 minutes the degree of chlorobenzene destruction was tested and the results of the analysis are presented in Table 7 below.

Table 7

Temperature (°C) 280 320 350

Residual Chlorobenzenes after 127.0 32.0 <0.01 180 minutes (mg/kg)

Example 8

In this example it is shown that the method of the invention may be employed to decompose a large range of halogenated organic compounds.

(a) 120 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of C16-C18 commercial grade aliphatic alcohol. To this mixture, 80 grams of crude hexachlorobenzene (HCB), having the composition shown in the first column in Table 8, was added. The reaction mixture was agitated vigorously and the temperature raised to 300°C. After 30 minutes at 300°C, a sample was taken from the mixture and analysed by gas chromatography - mass spectroscopy. The results of analysis at time 30 minutes are presented in the second column of Table 8. The temperature was then raised to 350°C and heat continued for a further 60 minutes. After this period a sample of the mixture was analysed by gas chromatography - mass spectroscopy. The results of the analysis at time 90 minutes are presented in the third column of Table 8 below.

Table 8

Amount (mg/kg)

Time Crude 30 90 (minutes) HCB minutes minutes

hexachloro benzene >900,000 4 - (90%) hexachloro ethane 13,800 - -

1,1,2,3,4,4 - - hexachloro butadiene 19,200 octachloro styrene 9,500 - - pentachloro benzene 275 42 - tetrachloro benzene 215 45 - trichloro benzene 135 9 -

2,4,5 tribromo toluene 125 - - decachloro biphenyl 1,700 - - dichloro benzene - 0.1 -

(b) 120 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 7 grams C16-C18 commercial grade aliphatic alcohol. The temperature of this mixture as raised to 270°C and then reduced to 250°C for the 'batch addition' of each of three batches of 20 grams crude pentachlorophenol (approximately 80%, total 60 grams pentachlorophenol added) . Other components in the crude pentachlorophenol mixture are listed in Table 8. The temperature of the mixture was then raised to 350°C for 180 minutes. At the completion of the reaction a sample of the mixture was analysed by gas chromatography - mass spectroscopy. No chlorinated compounds including chlorinated phenols, chlorinated dioxins or chlorinated furans were detected.

2378 TCDF 0.5 mg/kg Non 2378 TCDF 1.9 mg/kg

2378 PeCDFs 5.8 mg/kg Non 2378 PeCDF 9.3 mg/kg 12378 PeCDD 0.05 mg/kg Non 12378 Pe CDD 0.03 mg/kg

2378 HxCDFs 26.5 mg/kg Non 2378 HxCDFs 186 mg/kg 2378 HxCDDs 63.3 mg/kg Non HxCDDs 63.1 mg/kg

2378 HpCDFs 27.8 mg/kg Non 2378 HpCDFs 62.2 mg/kg 2378 HpCDDs 261 mg/kg Non 2378 HpCDDs 82.8 mg/kg

OCDF 7.1 mg/kg OCDD 19.1 mg/kg

Notation:

CDF = chloro dibenzofurans CDD = chloro dibenzodioxins

T = tetra

Pe = Penta

Hx = Hexa

Hp = Hepta

0 = Octa

Example 9

In this example, four further illustrations of a typical procedure for decomposing PCBs are provided. In each part of this example, a different aliphatic alcohol is used. Each of the aliphatic alcohols has a non-polar hydrocarbon tail.

(a)

180 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of 1-hexadecanol. To this mixture, 193 grams of PCB was added. The reaction mixture was agitated vigorously and the temperature raised to 350°C. The degree of PCB destruction was tested at regular intervals. The results of the PCB analysis are presented in Table 9(a) below.

Table 9(a)

Time (minutes) % PCB Destruction

10 41.3

40 65.7

160 91.2

310 >99.9

(b) 90 grams of sodium hydroxide was added to a mixture of 400 grams hydrocarbon oil and 5 grams of 1,2- hexadecanediol. To this mixture, 100 grams of PCB was added. The reaction mixture was agitated vigorously and the temperature raised to 350°C. The degree of PCB destruction was tested at regular intervals. The results of the PCB analysis are presented in Table 9(b) below.

Table 9(b)

Time (minutes) % PCB Destruction

30 72.8

150 98.1

240 >99.9

(c)

90 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of 1-dodβcanol. To this mixture, 100 grams of PCB was added. The reaction mixture was agitated vigorously and the temperature raised to 348°C. The degree of PCB destruction was tested at regular intervals. The results of the PCB analysis are presented in Table 9(c) below.

Table 9(c)

Time (minutes) % PCB Destruction

30 71.8

180 97.1

(d)

90 grams of sodium hydroxide was added to a mixture of 450 grams hydrocarbon oil and 5 grams of 1-docosanol. To this mixture, 100 grams of sodium hydroxide was added. The reaction mixture was agitated vigorously and the temperature raised to 352°C. The degree of PCB destruction was tested at regular intervals. The results of the PCB analysis are presented in Table 9(d) below.

Table 9(d)

Time (minutes) % PCB Destruction

20 61.7

160 93.3

In the foregoing experiments, it was observed that the halogenated organic compounds were decomposed directly to carbon without the production of any intermediate non- halogenated hydrocarbon compounds. At best, only trace levels of dehalogenation products were detected early in the reaction, and it is believed that the appearance of trace levels of these compounds was due to unavoidable minor side reactions and thermal degradation under the conditions of the reaction.

The results of examples 1-9 set out above illustrate that the method of the present invention is capable of achieving high degrees of decomposition of PCBs and other halogenated organic compounds in relatively short periods of time (when compared with the known methods) without the addition of catalysts.

Many modifications may be made to the preferred embodiments of the method of the present invention without departing from the spirit and scope of the present invention.

Claims

CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for decomposing halogenated organic compounds comprising:

(a) forming a reaction mixture comprising:

(i) halogenated organic compounds;

(ii) an alkali hydroxide;

(iii) an organic solvent;

(iv) an aliphatic alcohol; and

2. The method defined in claim 1 wherein the temperature of heating step (b) is greater than the melting point of the alkali hydroxide.

3. The method defined in claim 2 wherein the temperature of heating step (b) is greater than 200°C.

4. The method defined in claim 3 wherein the temperature of heating step (b) is greater than 250°C.

5. The method defined in claim 4 wherein the temperature of heating step (b) is greater than 300°C.

6. The method defined in claim 1 wherein the organic solvent has a boiling point greater than the temperature of heating step (b) .

7. The method defined in claim 1 wherein the organic solvent is a hydrocarbon oil.

8. The method defined in claim 1 wherein the alkali hydroxide is selected from the group comprising sodium hydroxide, potassium hydroxide, and lithium hydroxide, or mixtures thereof.

9. The method defined in claim 1 wherein the aliphatic alcohol has a non-polar hydrocarbon tail.

10. The method defined in claim 1 wherein the aliphatic alcohol has at least 9 carbon atoms.

11. The method defined in claim 10 wherein the aliphatic alcohol has no more than 22 carbon atoms.

12. The method defined in claim 1 wherein the aliphatic alcohol is an unbranched aliphatic alcohol.

13. The method defined in claim 1 wherein the aliphatic alcohol has only one OH functional group.

14. The method defined in claim 1 wherein the method further comprises a step in which the halogenated organic compounds are extracted from a contaminated material prior to steps (a) and (b) .

15. The method defined in claim 1 wherein the halogenated organic compounds comprise polychlorinated biphenyls. AMENDED CLAIMS

[received by the International Bureau on 04 January 1996 (04.01.96); original claims 6-15 amended; remaining claims unchanged (2 pages)]

CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for decomposing halogenated organic compounds comprising:

(a) forming a reaction mixture comprising:

(i) halogenated organic compounds;

(ii) an alkali hydroxide;

(iii) an organic solvent;

(iv) an aliphatic alcohol; and

3. The method defined in claim 1 or 2 wherein the temperature of heating step (b) is greater than 200°C.

6. The method defined in any one of the preceding claims wherein the organic solvent has a boiling point greater than the temperature of heating step (b) .

7. The method defined in any one of the preceding claims wherein the organic solvent is a hydrocarbon oil.

8. The method defined in any one of the preceding claims wherein the alkali hydroxide is selected from the group comprising sodium hydroxide, potassium hydroxide, and lithium hydroxide, or mixtures thereof.

9. The method defined in any one of the preceding claims wherein the aliphatic alcohol has a non-polar hydrocarbon tail.

10. The method defined in any one of the preceding claims wherein the aliphatic alcohol has at least 9 carbon atoms.

11. The method defined in any one of the preceding claims wherein the aliphatic alcohol has no more than 22 carbon atoms.

12. The method defined in one of the preceding claims wherein the aliphatic alcohol is an unbranched aliphatic alcohol.

13. The method defined in any one of the preceding wherein the aliphatic alcohol has only one OH functional group.

14. The method defined in any one of the preceding claims wherein the method further comprises a step in which the halogenated organic compounds are extracted from a contaminated material prior to steps (a) and (b) .

15. The method defined in any one of the preceding claims wherein the halogenated organic compounds comprise polychlorinated biphenyls.