DK169377B1 - Process for Destruction of Halogenated Aryl Compounds - Google Patents

Abstract

A process for the destruction of halogenated products and more particularly of chlorinated aromatic products or of oils containing these products, for example unchlorinated dielectric fluids contaminated with PCBs. The process is characterised in that these products are subjected to the action of an alcoholate and preferably sodium methylate at a temperature of between 250 and 290 DEG C.

Description

in DK 169377 B1

The present invention relates to a process for the destruction of halogenated aryl compounds contained in a non-halogenated organic product such as a polyaryl alkane or a mineral oil.

5

It has already been proposed in the prior art to remove the PCBs contained in the electric transformer oils or in lubricating oils by extraction with methanol (U.S. Patent No. 4,387,018).

The methanol is then separated from the PCB by distillation and then recycled. This method allows the amount of PCB to be reduced by 70%. European patent specification EP 99 951 discloses the treatment of similar products with sodium in dispersion of particles 15 greater than 10 μπι. In European patent application no.

EP 107 404 discloses the treatment of a transformer oil containing 652 ppm PCB with sodium salts of a polyethylene glycol. These processes have the disadvantage of necessitating separations and recirculation or sodium handling. In European patent application no.

EP 21,294 discloses the destruction of dioxins in particular by chlorinated anisols containing 39.7 ppm 2,3,7,8-tetrachlorodi-benzo-p-dioxin, thereby reacting these products under pressure with sodium sheath to methanol at 160 ° C. Another 25 is explained in an article by Gyula Pfeifer and Terez Flora in Hungarian magazine MAGY. KEM. FOLYOIRATE 71 (8), 343-6 (1965) that sodium methylate may begin to decompose between 120 ° C and 140 ° C.

30 EP-225 849 describes the destruction of chlorinated organic compounds by adding them to a solvent which is then added to sodium and an alcohol. After the destruction, after extraction, the solvent can be reused for a subsequent destructive treatment.

EP-250 748 (priority date: June 25, 1986, publication date; January 7, 1988) relates to the purification of an oil for the purpose of removing chlorinated organic impurities using alcohols soluble in the oil.

Surprisingly, a much simpler and very effective approach has now been found.

Thus, the present invention relates to a process for the destruction of halogenated aryl compounds contained in a non-halogenated organic product such as a polyarylalkane or a mineral oil, the process of which is: a) contacting the products with at least one anhydrous alkali metal alcoholate in powder form; sufficient time for the organically bound halogens to be converted to inorganic halides; b) the amount of alcoholate is in excess of the stoichiometric amount based on the amount of halogen; c) the alcoholate is selected from sodium, d) that the temperature is higher than 220 ° C and e) that the non-halogenated organic product is recovered by distillation.

30

In particular, the invention relates to a process for the destruction of compounds containing aryl in spherical carbon atoms substituted by chlorine and / or bromine. One finds within this family e.g. chlorinated or brominated dioxins, chlorinated or brominated dibenzofurans, (polychlorine) biphenyls, (polybromo) biphenyls, (polybromo) diphenyl ethers, (polychlorine) diphenyl ethers and the compounds of claim 3.

Although the invention enables the destruction of any halogenated aryl compound, it is most advantageously implemented for products containing less than 1% by weight of halogen, preferably less than 1000 ppm.

Preferably, powdered sodium methylate is used.

Since the stoichiometry is one alcoholate group per halogen atom to be removed, an excess alcoholate amount is used relative to this stoichiometry. A very good dehalogenation is obtained, using an excess of 5-10 times the stoichiometric value. For example, if a mixture contains PCB in an amount of 100 ppm expressed as chlorine, a sodium methylate amount of 0.14% is used.

The scope of the present invention will not be exceeded by adding with the alcoholate another product which can convert the organic chlorine to inorganic chlorine such as e.g. sodium carbonate or another alkaline agent.

Advantageously, the contacting between the halogenated organic aryl compounds and the alcoholate is carried out with stirring e.g. in a stirred reactor or in a filled column, or any other device which allows sufficient stirring to ensure that the alcoholate is well distributed and in contact with halogenated compounds for the time necessary for the destruction thereof. The reaction can be carried out continuously or discontinuously. The kinetics of the reaction increase with temperature. A temperature between 220 ° C and 300 ° C can be used, preferably between 250 ° C and 290 ° C.

35 Depending on the physical properties of the products concerned (vapor pressure) at atmospheric pressure or under higher pressure. The duration of the reaction is a function of the amounts of organic halogen, of the temperature, of the amount of alcohol, and of the stirring conditions to effect a good contact formation between the reaction components. The value is usually between 30 minutes. and 10 hours.

The present invention is particularly useful for destroying halogenated aryl products contained in a mixture e.g. of a non-halogenated dielectric fluid or a mineral oil containing PCB. In connection with such a product containing PCB compounds or other chlorinated compounds, the method according to the invention is used, whereby, e.g. by distillation the inorganic halogenated products of the other products. In this way, a mineral oil or a dielectric liquid which is free of organically bound chlorine is obtained.

To be sure to perform as complete dehalogenation as possible, an excess of the alcoholate is used. When treating a dielectric liquid containing several hundred ppm of chlorinated aryl compounds, at the end of the reaction, the dielectric liquid, sodium chloride NaCl, the conversion products for the aromatic chlorinated products and the remainder of the unreacted alcoholate are obtained. It is very convenient to distill this mixture to recover the pure dielectric liquid which contains no more aromatic chlorine. It is wise when the alcoholate used is sodium methylate that one does not exceed the residence times of the 12 hour distillation apparatus at 295 ° C to avoid decomposition of the methylate.

The process of the present invention is also used to supplement a process with sodium carbonate. Sodium carbonate is very easy to handle? but it only allows the removal of aliphatic halogens as well as the most labile aryl halogens.

5 DK 169377 B1

The process of the invention makes it possible to obtain a product having an aryl halogen content less than 10 ppm. The advantage of this process is that, although applied to products containing the halogen atoms, which are only slightly reactive, it does not require the use of solvents. Ie that it is sufficient to add an alcoholate e.g. to the oil containing the PCB compounds without being required to add in addition to the alcoholate the alcohol corresponding to the alcoholate, as disclosed in European Patent No. 21,294. This procedure does not require, at the end of the treatment, before the products are recovered. for aryl halogens, to pre-separate the excess alcoholate, especially the sodium methylate.

15

Another advantage of the present process is that the by-products formed, such as sodium chloride NaCl, the compounds formed in the reaction between the halogenated aryl compounds and the alcoholate, and the remainder of the non-reacted alcoholate, can be easily destroyed by combustion without giving rise to toxic product formation.

The following examples further illustrate the invention.

EXAMPLE 1

1000 g of dibenzyltoluene (DBT) containing 300 ppm of aromatic chlorine in the form of monochlorobenzyltoluene is taken. This mixture is placed in a reactor equipped with a rotary agitator, an upwardly rising cooler and a nitrogen injection device. After rinsing for 15 min. with a nitrogen stream of 100 ° C, 1% by weight (i.e. 10 g) of sodium methylate is added. The medium is heated to reflux at 285 ° C with stirring and flushing with nitrogen for 3 hours. The product is then distilled under progressive creation of a vacuum up to 2 mm of mercury in such a way as not to exceed 300 ° C at the bottom of the column. The resulting distillate has a total aromatic chlorine content of 3 ppm.

By comparison, by treating the same product containing the same chlorinated products with sodium carbonate, a product having a total aromatic chlorine content of the order of 100 ppm is obtained.

EXAMPLE 2

DBT is treated analogously to Example 1, but using NaOC2H5, KOCHg, COC2H5, NaOCH (CH3) 2 under the same conditions as described in Example 1. The results thus obtained are shown in the following table.

EXAMPLE 3 a) DBT containing 1000 ppm PCB is treated for 3 hours at 280 ° C with 1% sodium methylate. A product containing less than 15 ppm chlorine is obtained.

b) Identical to a) except that DBT contains 25 1000 ppm tetrachlorobenzyltoluene.

The results obtained are set out in the table below.

EXAMPLE 4 a) A mineral oil containing 1000 ppm PCB is treated for 3 hours at 280 ° C with 1% CHgONa. A product containing less than 15 ppm halogen is obtained.

b) Identical to a) with the exception of £ that the mineral oil contains 1000 ppm octabromobiphenyl.

X0 The results thus obtained are shown in the following table.

EXAMPLE 5 15 A reactor equipped with a rotary agitator, a cooler and a nitrogen inlet was placed in 1600 g of DBT and 32 g of sodium methylate. The mass is heated to reflux (290 ° C) under flow with nitrogen and stirring. The nitrogen stream 20 is then stopped and the exhaust pipe from the cooler is connected to a water tank. After treatment for 70 hours at 290 ° C, no release of gases is observed. After cooling and filtration, the reaction medium shows that no light products in the filtrate as shown by chromatographic analysis show that the IR spectrum of the solid after washing with monochlorobenzene, with hexane and drying in the absence of air 30 (collected weight = 95% by weight of the methylate used) is exactly sodium methylate.

35 DK 169377 B1 8

Table I-1-1-1

| The nature of the treatment | Alko applied | Weight content of J

5 | light product | holat | halogen in the be-J

j | j acted and de- | | | | styled pro- | | | | cloth | I-1-1-1 10 In Example 2 | | | In DBT + 300 ppm In 1% C2H50Na | <15 ppm | In chlorine in the form of | 0.5% CH 2 OK [<15 ppm | In monochlorobenzyl- | 0.5% C <15 ppm | In toluene 10.5% (CH3) 2CHONa | 37 ppm |

15 I I I I

In Example 3 | | | I BT 100 + 1000 ppm I | | In PCB (6.5 Chlorine) | 1% CH ^ ONa | <15 ppm [I BT 100 + 1000 ppmI | | In tetrachlorobenzyl-1 | | In toluene In 1% CH ^ ONa | <15 ppm |

I I! IN

In Example 4 | | j I Mineral Oil + | | | 25 I 1000 ppm PCB | | | In 6.5 Chlorine (*) j 1% CH30Na j <15 ppm | In Mineral Oil + J | | In 1000 ppm octo- | j j I bromobiphenyl (1) | 1% CH30Na | <15 ppm | 30 1-1-1-1 (*) Measurement in the distillation residue of 580 ppm chlorine in the form of chloride calculated in relation to the amount of oil used.

35 Measurement in the distillation residue of 846 ppm bromine in the form of bromide based on the amount of oil used.

Claims (6)

A process for destroying halogenated aryl compounds contained in a non-halogenated organic product, such as a polyaryl alkene or a mineral oil, characterized in: a) contacting the products with at least one anhydrous alkali metal alcoholate in powder form for a sufficiently long period of time; time for the organically bound halogens to be converted to inorganic halides; b) the amount of alcoholate is in excess of the stoichiometric amount based on the amount of halo gene; c) the alcoholate is selected from sodium, lithium or potassium methylate. , ethyl acetate, propylate or isopropylate, d) the temperature is higher than 220 ° C, and e) the non-halogenated organic product is recovered by distillation. Process according to claim 1, characterized in that the halogenated aryl compounds contain aryl carbon atoms which are substituted by chlorine and / or bromine. Process according to claim 2, characterized in that the compounds containing aryl carbons are benzyltoluenes or triphenylmethanes or higher homologues thereof. DK 169377 B l Process according to claim 2, characterized in that the compounds containing aryl hydrocarbons are PCBs, dioxins or dibenzofurans. Process according to any one of claims 1-4, characterized in that the temperature is between 220 ° C and 300 ° C, preferably between 250 ° C and 290 ° C. Process according to claims 1-5, characterized in that the alcoholate is preferably sodium methylate. 15 20 25 30 35