CA1181771A

CA1181771A - Process for dehalogenation of organic halides

Info

Publication number: CA1181771A
Application number: CA000408116A
Authority: CA
Inventors: James S. Ferrie; W. John Janis; Jean-Marie Braun
Original assignee: Ontario Hydro
Current assignee: Ontario Hydro
Priority date: 1982-07-27
Filing date: 1982-07-27
Publication date: 1985-01-29
Also published as: JPS5920179A; EP0099951A1

Abstract

ABSTRACT OF THE DISCLOSURE

Halogenated species such as PCB dissolved in hydrocarbon-based oils such as electrical insulating oils, turbine oils and crankcase oils are dehalogenated by contacting the oil with a fine dispersion of molten sodium particles of which at least 80% are below 10 microns particle size, at a temperature of 100 to 160°C. The process removes hazardous halogenated species and, after separation of excess sodium suspended solids and, if necessary, water washing, drying, and activated clay treatment, may permit the oil to be re-used.

Description

7~

PROCESS FOR DEHALOGENATION OF ORGANIC HALIDES

Polychlorinated biphenyls (PCB) have been identified as environmental hazards and possible carcinoyens. Thexefore the manufacture and sale of these materials in some territories, e.g. North America, is now prohibited. Fluids contaminated in excess of 25 mg/kg with PCB are considered environmentally hazardous and need to be stored until such time as a PCB de-struction facility is available. Considerable resources are being expended in the containment and monitoring of PCB and PCB contaminated wastes, both liquid and solid.

Proposed cornbustion methods for waste disposal will, if adopted, result in the sacrifice of large volumes of oils such as premium quality insulating oils having an economic value.
There is thus a need for a process which is capable of selec-tively destroying PCB in oils such as electrical insulatingoils without adversely affecting the important physical and el-ectrical properties of the oil.

This invention relates to a process for the dehalogena-tion (destruction) of polychlorinated biphenyls and polychlor-inated benzenes such as are found in electrical insulating oilscontaminated with compounds generically classified as askarels.
The process of the invention can also be used to decontaminate PCB contaminated solid wastes using oil as a solvent andtor for 7~

the destruction oE concentrated PCB waste liquids by dilution in oil.

The process disclosed hereinafter may more generally be applied to the dehalogenation and destruction of organic halides including hazardous halogenated was-tes such as organic halide-containing wood preservatives and pesticides.

It is known from an article by A.~. Morton et al "Condensation by Sodium Instead of by the Grignard Reaction III. Tertiary Carbinols and Acids" JACS, Soc 53, pages 402~
- 4033 (1931) that chlorobiphenyl may be reacted with metallic sodium, in the form of sodium wire or ribbon, under ice cold conditions or with gentle warming, in the presence of ethyl carbonate or ethyl benæoate, with or without additions of ben~
zene, to obtain low or medium yields of biphenylcarbinols.

It is also known from R.L. Menville et al "Determination of Organic Halides with Dispersed Sodium" Anal Chem 31, pages 1901 - 2 (1959) that organic halides may be reacted with "dis-persed sodium", (which may be prepared as described in Moeller, T., ed., "Inorgan:ic Synthesis" Vol V, p.6 McGraw Hill, New ~ork, 1957) in solvents such as benzene, toluene, and xylene, to give quantitative yields of water-extractable halides.

It has, however been reported by Pytlewski L.L., et al., Proc. 6th Annual Symposium on Treatment of Hazardous Waste, EPA
Report EPA-600/9-80-011 (Sept. 1980) that whereas vigorousiy stirred solutions of sodium in polyethylene glycol dechlorinate organic chlorides at temperatures above the melting point of liquid sodium (97.28C), dechlorination does not occur when the polyethylene glycol is replaced by non-polar, low volatility ~ liquids such as Nujol~a relatively highly viscous non-polar white paraffinic mineral oil of petroleum origin).

Further it has been reported by Parker D.K., e-t al.~
Unnumbere~ Research Report, G~odyear Tire and Rubber Co., 7~
~ 3 --Akron, Ohio, (August, 19~0) that metallic sodium treatment of heat transfer hydrocarbon oils contaminated by 76 ppm PCB does not reduce the PCB content below about 49 ppm even after heat~
ing for 6 hours unless the mixture is heated to a tempera-ture of 300C.

It has now been found that organic halides dissolved in hydrocarbon-based oils may be effectively dehalogenated at tem-peratures ranging from about 100C up to about 160~C by main-taining the solution under agitation in a mixture with a fine dispersion of molten sodlum particles of which at least 80% are below 10 microns particle size, whereby the organic halide groups are reduced to sodium halide.

In the preferred form, the fine dispersion of mol-ten sodium particles is formed by pre-dispersing metallic sodium un-der vigorous agitation in a relatively smaller quantity of ahydrocarbon-based oil the same as or compatible with the oil to be treated, at a temperature above the melting point of sodium and preferably in the range 105C to 160C, and the pre-disper-sion is added to the bulk of the oil containing the organic halide to be dehalogenated.

Of particular interest for present purposes is the treat-ment of electrical insulating oils contaminated with organic halides. When the present process is applied to such oils, it has been found that the resulting reaction mixture, after re-moval of unreacted sodium, suspended reaction products andsludges and, if necessary, water-washing, drying and activated clay treatment, has electrical and physical properties which render it re-usable as electrical insulating oil.

The process is also applicable to other hydrocarbon-based oils such as turbine oils and crankcase oils. In the case of treatment of used crankcase oilsl however, the treatmènt is accompanied by a significant increase in viscosity which ren~ -ders the application of the process more difEicult.

'7~7~

The present invention will now be more fully described, by way of example only, with reference to the accompanying drawings which show schematically one form of apparatus for carrying out the dehalogenation process.

In order to obtain a satisfactory degree of dehalogena-tion of the organic halides, it has been found necessary to react the organic halides wi-th a very fine dispersion of mol-ten sodium particles. In this very fine dispersion, at least 80~ of the sodium particles should be below 10 microns parti-cle size. More preferably, at least 90~ of the particles should be below about 10 microns and at least about 65~
should be less than 5 microns particle size. These very fine dispersions are best prepared by pre-dispersing sodium at temperatures above its melting point in a relatively smaller 15 volume of the oil to be treated, or an oil compatible there- _ with and which will not render the eventual product unusable for its intended purpose. The resulting very fine dispersion is then blended with a larger volume of contaminated oil, in order ~o provide a reaction mixture containing a desired ratio of sodium to reducible organic halide. ~ttempts to form the fine dispersion direct:ly, by vigorous agitation of sodium metal introduced into t:he bulk of the oil to be treated, are subject to the disadvanta~e that it may be impossible to form a dis-persion of the desired degree of fineness without incorporating excessive quantities of sodium into the mixture, and without prolonged agitation at very high shear rates, thus leading to excessive consumption of sodium and wastage of power required for agitation of the bulk of the oil to be treated.

In the preferred form, in order to form the pre-dispersion~
lump metallic sodium or liquid metallic sodium is added to dried oil in a quantity suficient to yield a dispersion contain-ing about 5 to 50~ by weight sodium. The use of less thall about 5% by ~eight sodium is usually inefficient, as then greater quantities of the pre-disyersion are required to achie~-e the desired molar ratios of sodium to reducible halogen, while with 7~
~ 5 --quantities of sodium much greater t]~an abou-t 50%, it is diffi-cult to achieve a satisfactory dispersion. Preferably, a weight of sodium sufficient to achieve an about 30% concentra-tion is employed.

The oil in which the pre-dispersion is to be formed may be a fresh, uncontaminated oil, or may be oil which is contam-inated with organic halide material. Desirably, in or~er to avoid excessive wastage of sodium, the oil is substantially dry and, if necessary, it is pre-dried either by heating or by vacuum degassification so that its moisture content is less than about 100 mg/kg. During the formation of the pre-disper-sion, the oil is maintained at a temperature above the melting point of liquid sodium, preferably in the range 105C to 160~C
Below about 105C, there is increased difficulty in obtaining a satisfactory dispersion, as the sodium particles tend to agglomerate together to form masses and it may not be possible to form a dispersion of the desired particle size range even with prolonged agitation. Temperatures much above about 160C
are undesirable, as there is an increased tendency for degrad-ation of the oil through thermal cracking and oxidation. Pre-ferably, the dispersion is formed at a temperature o~ about 120C.

The vessel in which the dispersion is formed, and all other vessels and processing equipment subsequently employed in the process with which the metallic-sodium-containing mix tures come into contact, are desirably formed or are lined with materials inert with respect to liquid sodium e.g. mild steel, stainless steel, or glass.

The mixture of sodium and oil is subjected to vigorous agitation for a period sufficient to produce a fine sodium dispersion of the required particle size distribution. The particle size distribution of the resulting dispersion can be readily determined usiny conventional optical particle counter apparatus, for example a HI-~C ITrade Mark) machine 7~7~

ancl the conditions of agitation and period of time required to produce the desired particle si~e distribution can be readily determined in any given case by trial and experiment. By way of examplel it may be mentioned that in the case oE disperslons containing 5 - 50~ by weight sodium, a satisfactory dispersion may be obtained after 10 - 15 minutes agitation in a modiEied one litre WARING (Trade ~ark) blender utilizing a bottom drive four blade impeller operated at 20,000 rpm. Alternatively, a top drive impeller equipped with either a Cowles Dissolver (Trade Mark) head or a Premier Mill Dispersator (Trade Mark) head may be used.

As noted above one preferred class of oils to be treated by the present process are contaminated electrical insulating oils. The properties of oils which are designated as "elec-trical insulating oils" are well understood by those skilled inthe art, and one skilled in the art can readily determine whether or not a given oil is an electrical insulating oil.
For the avoidance of doubt, as used herein the term "electrical insulating oil" refers to mineral electrical insulating oils of pe~roleum origin for use as insulating and coolin~ media in electrical power and distribution apparatus such as transfor-mers, regulators, reactors, circuit breakers, switch gear, and attendant equipment.

Desirably, electrical insulating oil should conform to the specifications set out in Table 1, as determined by the rele-vant ASTM test procedures. Preferably, the oils employed in the present process conform to these specifications.

Dielectric strength - more than 20 kv ~at water (ASTM D 877) content less than 20 mg/kg) Relative density at 15C - 0.8 to 0.92 (ASTM D 1298) Pour Point - -60C -to -10C

'7'~

Viscosity at 40C - 8 to 14 centistokes (ASTM D 445) Flash point - 140 to 200C
(ASTM ~ 92) A Eurther example of a class of oils which may be treated by the present process is turbine oil. These are usually sulfur-free mineral oils of petroleum origin employed as a lub-ricant medium in steam turbines, electrical generators and other rotating equipment systems. Preferably, the turbine oils conform to the specifications set out in Table 2.

Pour Point -40 to 0C
Viscosity at 40C
(ASTM D 445) 25 to 70 centistokes Flash Point (ASTM D 923 180 to 250C

A further example of a class of oils to which the process may be applied i5 crankcase oil i.e. oil used as internal com-bustion engine lubricant. Preferably, these conform to the specifications set out in Table 3.

Viscosity at 100C
(ASTM D 445) 4 to 20 centistokes Viscosity at -18C
(ASTM D 445~ ~ 9600 centistokes Flash Point (ASTM D 92) 150 to 240C
Pour Poin~ -50 to -5C

The dehalogenation of organic halides by fine liquid sodium particles does not occur satisfactorily in silicone-based electrical insulating oils and therefore in -the present process hydrocarbon-based oils are employed.

7~

In one e~ample of a process in accordance with the invention, as illustrated in the accompanying drawings, PCB-con-taminated electrical insulating oil or other hydrocarbon-based oil -to be treated is stored in a storage vessel 10 from which a batch of -the oil is transferred by a pump Pl along a line 11 to an enclosed reactor vessel 12 preferably of steel. The vessel 12 is equipped with a low speed impeller 13, heaters 14, and an exhaust condenser 16. A line 17 is provided connected to a cylinder 18 of nitrogen or other inert gas which is slowly bubbled into the mixture to exclude air and form a blanket of inert gas to reduce losses of the subsequently-introduced sodium through oxidation. The condenser 16 removes organic vapours from the exhaust nitrogen or other inert gas To avoid excessive production of hydrogen gas on addition of the sodium, and to avoid excessive sodium consumption, the oil in the storage vessel 10 is desirably pre-dried, if necessary, to less than 100 mg/kg water either by heating or by vacuum degassification.

With the batch of oil in the vessel being maintained under moderate stirring sufficient to ensure intimate mixing and to preven-t settling of the sodium dispersion, the pre-dispersion, prepared as described above is introduced into the reactor through a line 19.

Before the introduction of the suspension, the oil contained within the reactor vessel 12 is heated to a temperature in the range of 100 - 160C. At temperatures below 100C, the reaction times needed for substantially complete reduction of the organic halide groups to sodium halide tend to be excessively long, and there is a risk of the liquid sodium particles tending to agglomerate together to form agglomerated masses. It is important that the dispersion of sodium particles should remain in the form of dispersed particles of fine particle size, as wi-th particles of greater size, the reaction is much less effective. Without wishiny to be bound by any theory, it is believed that the reduction in -the rate and efEiciency of the dehalogenation process 7 9~
_ 9 _ with particles o~ increased size is due to the coating of such large particles by reaction products thus hindering or preventing ~urther reaction. In any event, it is -found that with larger sodium particles, for example of 100 microns particle size, the dehalogenation process is mu~h less effective. The use of a dispersion such that at least 80% of the particles are below 10 microns particle size, more preferably with at leas-t about 50% of the particles below about 5 microns particle size, is a hiyhly important factor in obtaining a satisfactory dehalogenation reaction. The oil in the reactor vessel should not be heated to temperatures much in excess of about 160C, as at higher temperatures t.here is increased risk of degradation of the oil through thermal cracking and oxidation. Preferably, the reaction mixture is maintained at a temperature of about 110C to about 130C.

Preferably, sufficient of the dispersion is added through the line 19 to the batch of oil isolated in the reactor 12 to provide in the reaction mixture a molar ratio of sodium to reducible chlorine in the range about 2:1 to 30:1. Below this range of sodium contents, satisfactory dehalogenation is not likely to be achieved, while contents of sodium higher than the above mentioned range do not appear to add to the effectiveness of the reaction and merely result in excessive consumption of sodium. In the most preferred form, the molar ratio of sodium to reducible halogen is at least about 4:1, and more preferably is about 4:1 to about 8:1.

Although oil solution containing greater than 10% by weight of dissolved halogenated species can be treated by the present process, greater quantities of the sodium dispersion need to be added to the oil and this may render it more difficult to maintain intimate mixing of the stirred reaction mixture. It is therefore normally preferred to employ oils containing no more than about 10~ by weight dissolved halogenated species. In the preferred form, the organic halide is a PCB and is present in the oil in an amount of at least about 25 mg/kg, more preferably at leas-t about 100 mg/kg. Employing the present process the oil can be sub-> -- 10 --stantially wholly dehalogenated to achieve final concentrations of organic halide species of less than about 5 mg/kg, more usually less than about 2 mg/kg wi-thin about 15 to 240 minutes.
In the preferred form, the dehalo~enation is comple-te in less than about 30 minutes.

On completion of the reaction, the ~eaction mixture is pumped by a pump P2 along a line 21 to a solids-liquids separa-tor device, for example a centrifuge Cl. Desirably, a centri-fuge capable of maintaining a minimum relative centrifugal force of 210 G at the periphery of the centrifugal plates is employed.
At -the centrifuge Cl, the solids i.e~ unreacted sodium, suspen-ded reaction products and sludges are removed from the oil. The removed solids are passed along a line ~2 and are collected in a collection vessel 23. If desired, the solids collected in the 15 vessel 23 may be subjected to a conventional treatment for re- _ covery of metallic sodium therefrom before being disposed of as waste.

The liquids separated at the centrifuge Cl may be passed along line 25 to a quenching vessel 24 where any remaining tra~
ces of sodium are quenched with water introduced through a line 26. If the oil has not cooled sufficiently through its passage through the centrifuge Cl, it is permitted to cool below about 95C before contact with the water, to avoid excessively vigor-ous reaction. In the vessel 24, the mixture of oil and water is maintained under agitation by a stirrer 27, and the oil is washed free of any remaining traces of sodium and of soluble reaction products such as sodium halide and sodium soaps of acidic oil components. The oil and water mixture is pumped by a pump P3 along a line 28 to a further centrifuge C2 where the heavier water phase is separated from the oil and collected in a waste water collection vessel 29.

The oil phase may be subjected to further washing stages and in such case is passed successively throu~h a series of washing tanks, similar to the quenching tank 24, where the oil '7'7~

phase is mixed with water, and the oil-water mixture Erom each tank is passed through a centrifuge similar to the centrifuge C2 be~ore passing to the subsequent washing tank. ~ single tank 24 for quenchiny and washing, and centriEuge C2, are suf-ficient for all washing stages if the oil phase is xeturnedto the washing tank 24 through a return line af-ter passing through centrifuge C2 The oil may be washed with a total volume of water appro~imately equal to that of the volume of the oil, and the washing may be conducted in 3 to 5 separate stages. As shown in the accompanying drawings, the first wash-ing stage in the tank 24 is desirably performed under a blanket of inert gas supplied along line 31 from the inner gas container 18, or may be conducted under copious air flow, to ensure that any hydrogen evolved in the reaction of sodium with water in the tank 24 is diluted to less than the lower explosive limit for hydrogen, more preferably to less than about one-fifth the lower explosive limit. Instead of subjecting the oil-water to centri-fugation after each washing stage, the mixture may instead be allowed to settle into distinct oil and water phases and the oil phase pumped off.

The gases evolved from the reactor vessel 12 and the quen-ching vessel 24 (mainly inert gas containing some hydrogen) are collected beneath exhaust hoods 32 and may be vented to the at-mosphere.

After washing, the oil is passed along line 33 to a storage tank 34. The washed oil is substantially free of halogen and halogenated compounds, but contains some dissolved water. The oil can be dried by pumping it by a pump P4 along a line 36 and filtering it through blotter type paper in a filter press 37 or 3Q by vacuum drying. The dried oil is collected in a vessel 38.
If necessary or desirable, the quality of the oil product may be further improved by filtering it through a column of acti-vated clay to remove trace impurities.

y~

The process described above may be modified by eliminating the quenching, water-washing and drying steps, without affecting the quality of the product if the solids separa-tion step is car-ried out efficiently. In such case, any remaininy sodium or suspended solids present in the product can be removed by ac-ti-vated clay trea-tment.

Some detailed Examples of the present process will now be given.

Sodium Dispersion Preparatio 25 g of lump sodium metal at 23C is added to the stainless steel mixing bowl of a 1 L capacity Waring Blender containing 300 g of an electrical insulating oil meeting standard specifi- _ cations for new electrical insulating oil. The oil is at a tem-perature of 120~C~ A nitrogen gas flow of approximately 60 ml/min is establislled over the oil to provide an inert atmos-phere, preventing oxidation of highly reactive sodium and the mixture is blended for 15 minutes at a controlled temperature of 122.5 ~ 2.5C and impeller speed of 20,000 RPM. The resulting mixture is a uniformly grey dispersion of spherical particles with particle size distributed as shown in Table 4.

The concentration of sodium in oil may be varied from about 5% to about 50% by weight.

Sodium Particle Distribution Data Particle Number Diameter Average of Range Particles in (~m~ Range (%
30 ~3 40 g-ll 1~
11-15 3.4 3515-30 0.6 The extreme ~ineness of the dispersion (65% of particles less than 5 ~ diameter and 96~ less than 11 ~m diameter) will be noted.

EXAMPLES 2 to 16 Dechlorination of Chlorinated ~romatics with Sodium Disl~_rsion _ Freshly prepared sodium dispersion prepared as described in Example 1 is used to dechlorinate several chlorinated com-pounds, intimately mixed with insulating oil, in a 1 L glass reactor consisting of a standard 3-necked flask equipped with a sealed stirrer, nitrogen gas input/output connections, four equally spaced 1/2" glass baffles and an electric heating ~an-tle. Reaction conditions and results for a variety of dechlor-inations are given in Table 5.

The results obtained are repeatable and consistent when using dispersions prepared in the manner disclosed above. Lar ger sodium particles, for example 100 ~n particles, are much less effective in promoting dechlorination and coating of such large particles by reaction products is suspected. The sodium particle size is thus an important factor in the efficient de c~lorination o PCB by molten sodium.

In example 16, the dechlorination was conducted on an oil sample containing an oxidation inhibitor, showing that the presence of oxidation inhibitor does not interfere with the dechlorination process.

EXAMPLES 17 to 19 Dechlorination of PCB and Chlorinated Benzenes with Sodium Dispersion , PCB contaminated insulating oil is treated in a 205 L re-actor system according to the method described above in detail with reference to the accompanying drawings. Oils used are ob-tained from segregated stocks of PC~ con-tamina-ted insulating oil from Ontario Hydro storage~ These stocks are contaminated wi-th 7 ~
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The results of three typical reactions usiny a batch size of 120 L are ~iven in Table 6. In all cases, PCB and chlorin-ated benzenes are effectively destroyed in the reaction step.
The efficiencies of the dechlorina-tions are more than -twice -those of the laboratory scale tests obtained in Examples 2 to 16 and it appears this is because at larger scale operation there is reduced air oxidation of the sodium and more effective contact of reactive sodium with the chlorinated organics.

Oil Reclamation To determine the overall effect of the PCB dechlorination reac-tion, water washing, and clay treatment on oil quantity, standard electrical insulating oil acceptance tests were per-formed on untreated, PCB-dechlorinated and final clay-treated oils. The oils used in these tests were obtained as follows:
(l) The untreated oil sample was new insulating oil meet-ing a standard electrical insulating oil specification ~Ontario Hydro specification M-104M-79).

(2) The PC'B dechlorinated oil sample resulted from treat-ment of 500 mg/kg Type D askarel in untreated oil with sodium followed by water washing and filter drying as described in detail above with reference to the draw-ings or by vacuum drying.

(3) The clay treated oil sample was obtained by agitating 1% by weight Fullers Earth with PCB dechlorinated oil at 70C using a laboratory bench stirrer for 1 hour.

- The results for the untreated, PCB-dechlorinated and clay treated oils are compared to new oil acceptance requirements in Table 7. Some of the quality tests were repeated after oxi-dation stability testiny which consisted of subjecting the oil to oxidizing conditions effective to remove oxidation stabili-sers from the oil. After PCB dechlorination, the power factor, _ ~ 7~
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1~ --OIL QUALITY TESTS

Test Reference Requirements Untreated PCB Final tASTM) ~Ontario HydroOil Dechlorinated Clay M104-79)Sample SampleTrOailed . ~ . _ ._ _ . . _ Steam Emulsion D1935 Max 60 25 63 59 Number (S) Water Content _ * 36 48 44 ~mg/kg) PCB Content OH Test 2 2 2 2 (mg/kg) Power Factor D924 Max 0.5 0~48 0.6~ 0.12 @ 100C ~%) Dielectric D877 Min 26 32 16 33 Strength (kV) Neutrallzation D974 Max 0.03 0.01 0.01 0.01 Number (mg ~OH/g) Interfacial D971 Mln 35 44 40 48 Tension (mN/m) Relative Density D1298Max 0.906 0.861 0.860 0.860 @ 15C
ASTM Colour Value D1500 Max 1 1.0- 2.0- 1.5 Pour Point (C) OH Test Max -46 -46 -46 -46 Viscosity @ D445 Max 10 9.0 9.2 9.1 37.8C ~mm~/S) Flash Point (C) D92 Min 146 157 157 157 Fire Point (C) D92 * 174 168 168 Oxidation D2440 Pass Pass Pass Pass Stability Results After Oxidation Stability Test Neutralization D974 Max 0.10 0.10 0.01 0.01 Number (mg ~O~/g) Interfacial Tension (mN/m) D971 Min 20.0 36.5 33.0 38.0 Sludge Nil Nil Nil Nil ASTM Colour Value D1500 2.5- 3.5- 2.5 .. _ * Not a requirement for acceptance.

7~

steam emulsion number, dielectric streng-th and colour value did not meet the requirements for new oil. Following clay treat-ment only the colour value failed to meet -the new oil requixe-- ment. The high colour value is not considered significant since the oil passed the tests for pour point, power fac-tor, dielectric strength, oxidation stability, and steam emulsion number. The final clav treated oil is considered suitable for use in transformers and other electrical equipment requiring an oil meeting standard specifications e.g. Ontario Hydro Specifi-10 cation M-104-M79 and/or CEA Standard C-50.

Examples 20 and 21 The process generally as described in Example 2 was re-peated using PCB-contarninated turbine oil. The results are as indicated in Table 8.

_ ~ _ _ Initial Reaction ~Reaction Sodium/Chlorine ¦ Final PCB TimeTemperature ratio l PCB
Content(hours) ~C) (mole/mole) ¦ Content (mg/kg) _ I (mg/kg3 ¦

650 1 _ 140 16/1 ~2 _ Example 22 -The process generally as described in Example 2 was re-peated using a PCB-contaminated used crankcase oil. The re-sults are shown in Table 9.

Initial Reaction Reaction Sodium/Chlorine Final PCB TimeTemperature ratio PCB
Content (hours) (C) (mole/mole) Content 30(mg/kg) (mg/kg3 __ _ __ 680 1 1~0 16/1 29 7~

~ 20 ~

'~he results show that a siyniEicant decrease in the organic halide content was obtained, but the increase in viscosity made it difficult to maintain adequate stirring of the reaction mix-ture and continue the reaction. Continued reaction using the same equipment, to ob-tain a product with a reduced PCB con-tent which could be sa~ely disposed of, could be obtained by using as a diluent other oil less suscep-tible -to an increase in viscosity under the reaction conditions~ Al-ternatively, the reaction could be carried out using equipment such as a roller mill in which continued agitation o~ the reaction mixture would not be hindered by the viscosity increase.

Claims

?HE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
?R PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Process for dehalogenation of organic halides comprising reacting the organic halide dissolved in a hydrocarbon-based oil, at a temperature of from about 100°C to about 160°C, under agitation, with a fine dispersion of molten sodium particles of which at least 80 are below 10 microns particle size, for a period sufficient to chemically reduce substantially all of the organic halide groups to sodium halide.

2. Process as claimed in claim 1 in which said temperature is about 110°C to about 130°C.

3. Process as claimed in claim 1 in which the reaction is conducted for a period of from about 10 to 240 minutes.

4. Process as claimed in claim 3 in which said period is less than 30 minutes.

5. Process as claimed in claim 1 in which the molar ratio of sodium to reducible halogen is from about 2:1 to about 30:1.

6. Process as claimed in claim 1 wherein an isolated batch of said oil containing the organic halide is reacted with an amount of said dispersion sufficient to achieve a molar ratio of sodium to reducible halogen of at least 4:1.

7. Process as claimed in claim 6 wherein said ration is no more than about 30:1.

8. Process as claimed in claim 6 in which said ratio is from about 4:1 to 8:1.

9. Process as claimed in claim 1, 6 or 7 wherein the oil comprises electrical insulating oil, turbine oil, crankcase oil, or a mixture thereof.

10. Process as claimed in claim 1 in which the oil is pre-dried to a water content of less than about 100 mg/kg.

11. Process as claimed in claim 1 in which the reaction is carried out under an inert gas blanket.

12. Process as claimed in claim 11 in which the inert gas is nitrogen.

13. Process as claimed in claim 1 including the steps of pre-dispersing metallic sodium at a temperature above its melting point under vigorous agitation in a relatively smaller quantity of a hydrocarbon-based oil the same as or compatible with the oil containing the organic halide to be dehalogenated, to achieve said fine dispersion, and subsequently blending the fine dispersion with the bulk of the oil containing the organic halide.

14. Process as claimed in claim 13 wherein the pre-dispersion is formed at a temperature of about 105°C to about 160°C.

15. Process as claimed in claim 13 or 14 wherein the pre-dispersion contains about 5% to about 50% by weight sodium.

16. Process as claimed in claim 13 wherein sufficient of the fine dispersion is blended with the bulk of the oil to achieve a molar ratio of sodium to reducible halogen of at least 2:1.

17. Process as claimed in claim 13 or 16 conducted as a batch process wherein the fine dispersion is added to, and the dehalogenation is conducted on a batch of the oil isolated in a reactor vessel.

18. Process as claimed in claim 1, 13 or 16 wherein the organic halide is a PCB present in the oil in an amount of at least about 25 mg/kg.

19. Process as claimed in claim 1, 13 or 16 wherein the organic halide is a PCB present in the oil in an amount of at least about 100 mg/kg.

20. Process as claimed in claim 1, 13 or 16 wherein at least about 50% of the sodium particles in the fine dispersion are below about 5 microns particle size.

21. Process as claimed in claim 1, 13 or 16 wherein at least about 90% of the sodium particles in the fine dispersion are below about 10 microns and at least about 65% are less than 5 microns particle size.

22. Process as claimed in claim 1, 13 or 16 wherein the organic halide is a chloride.

23. Process as claimed in claim 1, 13 or 16 wherein the organic halide is a PCB.

24. Process as claimed in claim 1, 13 or 16 wherein the organic halide comprises a halogenated wood preservative or pesticide.

25. Process as claimed in claim 1, 13 or 16 wherein the organic halide is present in the reaction mixture in a concentration of up to about 10% by weight, based on the weight of the mixture.

26. Process as claimed in claim 1 wherein the reaction mixture is subjected to a solids separation step to remove unreacted sodium, suspended reaction products, and sludges, and the oil obtained is recovered.

27. Process as claimed in claim 26 wherein said solids separation is conducted by centrifugation.

28. Process as claimed in claim 26 wherein the liquid is water washed to remove sodium and water-soluble reaction products and the oil phase is recovered.

29. Process as claimed in claim 28 wherein the oil phase is subjected to a drying step.

30. Process as claimed in claim 26, 27 or 29 wherein the oil obtained is subsequently purified by treatment with activated clay.

31. Process for dehalogenation of organic halides, comprising the steps of pre-dispersing sodium metal in a relatively smaller quantity of hydrocarbon-based oil under vigorous agitation at about 105°C to 160°C to achieve a fine dispersion of molten sodiumparticles of which at least 65% are less than about 5 microns and at least 90% are less than about 10 microns particle size, and containing about 5 to 50% by weight sodium, providing an isolated batch of a relatively larger amount of hydrocarbon-based oil comprising electrical insulating oil, turbine oil, crankcase oil or a mixture thereof and being the same as or compatible with the first-mentioned oil and having dissolved therein up to about 10 by weight of organic halide, mixing with said isolated batch an amount of said pre-dispersion sufficient to achieve a sodium to reducible halogen ratio of from about 4:1 to about 30:1, and maintaining the mixture under agitation at a temperature of from about 100°C to about 160°C for a period of from about 10 to 240 minutes sufficient to reduce substantially all of the organic halide groups to sodium halide.

32. Process as claimed in claim 1, 13 or 31 wherein the oil is a turbine oil.

33. Process as claimed in claim 1, 13 or 31 wherein the oil is a turbine oil which is substantially sulfur-free and conforms to the following specifications:
Pour Point -40 to 0°C
Viscosity at 40°C 25 to 70 centistokes (ASTM D 445) Flash Point 180 to 250°C
(ASTM D 92)

34. Process as claimed in claim 1, 13 or 31 wherein the oil is a crankcase oil.

35. Process as claimed in claim 1, 13 or 31 wherein the oil is a crankcase oil conforming to the following specifications:
Viscosity at 100°C 4 to 20 centistokes (ASTM D 445) Viscosity at -18°C ? 9600 centistokes (ASTM D 445) Flash Point 150 to 240°C
(ASTM D 92) Pour Point -50 to -5°C