NZ223232A - Destroying chlorinated organic products using chloroaluminates - Google Patents

Abstract

1. Process for destroying chlorinated organic products containing more than 2 carbon atoms, in which these products are brought into contact with a bath of at least one chloroaluminate, characterized in that the initial concentration of the chlorinated organic products in the bath is 4000 ppm or less and preferably 2000 ppm or less.

Description

New Zealand Paient Spedficaiion for Paient Number £23232 . •' . . . 1A .' ..yZSH' ■ - r- '.'x J,,., ^ NO DRAWINGS Priority Date(s): ... ^.V. ).'&! Complete Specification Filed: ......9^r.

Classr /<5Cr Publication Date: ^.8. .MAY. .193) P.O. Journal, Nor.... 16A.V i.

NEW ZEALAND 22 3 2 3 2 N/43383 \J *f& ■ THE PATENTS ACT 1953 PATENTS FORM NO. 5 COMPLETE SPECIFICATION "PROCESS FOR DESTROYING AT LEAST ONE CHLORINATED PRODUCT CONTAINING MORE THAN TWO CARBON ATOMS" WE, ATOCHEM, a French body corporate (France) of La Defense , 4 & 8 Cours Michelet, 92800 PUTEAUX, France, hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 - (followed by page la) \ 22 3 2 3 2 - l PROCESS FOR-&SSTROYIMC AT LEAST ONE CHLORINATED PROB3€T CONTAINING MORE THAN TWO CARDOH ATOMS The present invention relates to a process for destroying at least one chlorinated organic product 5 containing more than 2 carbon atoms and more particularly chlorinated aromatic products and polychlorobiphenyls.

Certain dielectric liquids contain chlorinated organic products and after a certain period of operation 10 they decompose and need to be replaced. It is sometimes possible to regenerate them completely or partially but it is often necessary to destroy a proportion of these liquids.

Chlorinated organic products, as well as certain pesticides and chlorinated aromatics such as hexachloro-15 benzene or polychlorobiphenyls (PCB) can give rise to toxic products when they are burnt like an ordinary flammable product.

In order to avoid generating toxic products these chlorinated products are destroyed at a high temperature 20 under specific conditions.

A paper in Sci. Total Environ. 1978, 10 (1) 51-9 describes the destruction of polychlorobiphenyls (PCB) by incineration with a residence time of more than 2 seconds.

Another paper, Proc. Ann. Meet - Air Pollut. Control 25 Assoc. 1977 (Vol 2) paper No. 33, describes a 99.9995% destruction of PCBs at 1000°C with a residence time of 2 223232 2 seconds.

European Patent EP 170,714 describes the destruction of PCBs by reaction with molten aluminium or an aluminium-based eutectic; the reaction takes place above 382° C.

A much simpler process for destroying these products, capable of operating below 3 00° C, has now been found according to the present invention.

The present invention provides a process for destroying chlorinated organic products containing more than 2 carbon atoms, characterised in that these products are placed in contact with a bath of at least one chloroaluminate (as hereinafter defined) at a temperature not exceeding 300° C, the quantity of chlorinated organic product being less than 5,000 ppm of the chloroaluminate.

Various chloroaluminates or their mixtures can be employed, for example, potassium, lithium, sodium, calcium, strontium or ammonium chloroaluminates. As used herein,*the name "chloroaluminate" is given to any mixture of anhydrous aluminium chloride and one or more metal chlorides.

"Sodium chloroaluminate", which is preferably employed, denotes a mixture of aluminium chloride and of sodium chloride in any proportions and not only an equimolar mixture. Sodium chloroaluminate may also contain lithium and/or potassium chlorides. It is therefore possible to have a mixture of aluminium chloride, sodium chloride and lithium chloride, which is called sodium lithium. u 223232 chloroaluminate.

It is also preferred that the sodium chloroaluminate should contain at least 50 mol% of aluminium chloride and should have a melting point below 200°C. 5 The invention applies to all chlorinated organic products containing more than 2 carbon atoms, but it is, first and foremost, usable in the case of aliphatic, cyclic, mono- or polycyclic aromatic and heterocyclic products, most especially perchlorinated aliphatic products and 10 polychlorobiphenyls. The quantity of chlorinated organic products is less than 5000 ppm of chloroaluminate and preferably less than 2000 ppm.

These products may be in any form. They may, in particular, be in a solid phase, for example absorbed on 15 active charcoal.

The process according to the invention consists in placing the chlorinated product in contact with the bath of chloroaluminate.

When the chlorinated product is in a solid phase, 20 this solid phase may be poured into the bath of chloroaluminate, preferably stirred. Care should be taken to keep the bath molten, by heating if necessary. The procedure is similar if the chlorinated products are in a liquid phase. In most cases the chlorinated products which 22 3 2 3 2 mixed with light chlorinated products and/or carrier gases. For example, the gas may be one produced by combustion, consisting of nitrogen containing carbon dioxide, carbon monoxide, chlorinated products and possibly oxygen.

However, it may be any gaseous mixture taken from any process.

It is preferable that the chlorinated products should be in an anhydrous phase. The gas containing the chlorinated products may be dried by contact with an 10 absorbent, for example alumina or glycol.

This gaseous phase containing the chlorinated products to be destroyed is then placed in contact with the chloroaluminate using any means for placing a liquid phase in contact with a gaseous phase. This may be a plate- or packed column. The gaseous phase may also be introduced into a stirred vat of chloroaluminate through a dip tube or through a tube entering via the bottom of the vat.

The various chlorinated organic products may partition between the liquid and vapour phases of the 20 chloroaluminate bath. Similar comments apply to the products which accompany these chlorinated products. A plate- or packed column may be employed in order to ensure continuous circulation and stirring of the liquid and gaseous phases and good contact between the gaseous products and the chloroaluminate bath. It is also possible to 22 3 2 32 operate using a cascade of stirred reactors. The chlorinated organic products are kept in contact with the chloroaluminate bath for the period required to destroy them. The residence time may vary within wide limits but is 5 generally from a few minutes to a few hours.

Although it is possible to operate at any temperature, provided that the chloroaluminate is liquid, it is preferable for this to be done at a temperature not exceeding 300°C and preferably at 200° to 300°C. 10 The rate of destruction of the chlorinated products, especially aromatic products, increases with the temperature of the chloroaluminate.

Light products of decomposition of the chlorinated products which it was intended to destroy may be found in 15 the gaseous phase of the chloroaluminate bath, for example carbon tetrachloride and/or hexachloroethane. The chlorinated organic products which it was intended to destroy are not to be found in the vapour phase of the chloroaluminate bath. When the chloroaluminate bath is 20 analysed after contact between the chlorinated products and the chloroaluminate, the organic products which it was intended to destroy are generally not found.

The chloroaluminate bath may also be purged at regular intervals to avoid the accumulation of products 25 which are insoluble or which cannot remain in suspension in 22 3 2 32 the bath.' Generally no trace of the chlorinated organic products is found in this purge either. It can be concluded, therefore, that the chlorinated products which it was intended to destroy have disappeared.

In a preferred embodiment of the invention, one or more powdered metals chosen from reducing metals such as aluminium or zinc, are added to the chloroaluminate bath. It is preferable to employ a powder whose mean particle size is less than 500 p. When metals are employed, the 10 chlorinated organic products can be completely eliminated as previously but at a markedly higher rate, of the order of several times to several tens of times the previous rate.

A consumption of the powdered metal (or metals) is observed, and this may mean that chloride has formed, taking 15 up chlorine from the chlorinated organic products. There is no limit to the quantity of metal powder to be introduced into the chloroaluminate. It is preferable to employ aluminium powder; typically up to 5 or 10% by weight of aluminium powder may be placed in the chloroaluminate bath. 20 it has been found that the rate of destruction of the chlorinated products increases with the quantity of aluminium powder and with the temperature of the chloroaluminate bath. It is preferable to stir the bath so that the metal powder is well dispersed in the bath. The 25 metal chloride or chlorides which have been produced may mix 22 3 2 3 2 with the chloroaluminate bath and may partition between the liquid and gaseous phases. If necessary, the metal chlorides may be removed from the gaseous phase by treating them with a hydroxide, such as sodium hydroxide or potassium hydroxide.

The following Examples further illustrate the present invention: EXAMPLE 1 500 g of sodium chloroaluminate in which the mole ratio AlClj/NaCl = 1 are introduced into an electrically heated 1-litre Pyrex round flask fitted with a propeller stirrer rotating at 300 rev/min. The product is heated to 200°C, stirred, and then 0.2 g of hexachlorobenzene and 0.1 g of decachlorobiphenyl are introduced. After 1 hour at 200°C, 22 32 3 2 the molten bath is purged for 15 minutes with a stream of SO l/h of N2/ which is washed in a bubbler containing 100 ml of hexane.

The chlorinated organic compounds in the final 5 bath and in the' hexane are determined by gas phase chromatography.

The results are shown in Table 1.

EXAMPLE 2 The same test is carried out, but 5X of fine alum-10 inium powder (Pechiney XY 49 grade) are additionally introduced into the chloroaluminate bath. After 1 hour at 200°C followed by purging with 50 l/h of N£ for 15 min, a sample of the bath and of hexane is taken for quantitative analys i s.

TABLE 1 ! ! ru.Scft ! WITHOUT Al ! WITH 5% Al INATED j j 0RGANIC ! I ! X of 1 I 1 X of PRODUCTS | BATH fhexane I product \ BATH f hexane J product 'I <. J { | removed .! j start jfinalj | j start ! ! 1 I ! I 1 ! C,C1, ! 200 till I 13.2 1 37.7 Z! 200 129 ! 3.5 ! 83.7 6 6 , ! 1 I 1 ! ! ! DCBP* I 100 141.3 ! 0.40! 58.3 Z! 100 1 3.8 ! 0.2 ! 96 ! ! ! I ! ! ! ! * OCBP: decachlorobiphenyl - Values in wg 22 3 2 3 2 EXAMPLE 3 The operation is carried out in the same apparatus as employed for Examples 1 and 2, but the operating conditions are changed: - bath temperature: 250°C - weight of the chloroaluminate bath: 500 g - addition of 5% of Al powder (Pechiney XY 49) - duration of the test: 2 hours - nitrogen purge after 2 hours: 15 min - initial addition of: 500 mg of hexachlorobenzene 500 mg of decachlorobiphenyI The results are given in Table 2.

EXAMPLE 4 Same test as in Example no. 3 but the duration of the test is 4 hours.

The results are shown in Table 2.

TABLE 2 ! CHL0R- J INATED j DURATION Z h DURATION 4 h ]ORGANIC f 1 1 * of;!;;;I;X of !;(PRODUCTS!;BATH {;hexane;(product!;BATH;[ hexane.! product];! 1;1 1;]removed |;1;!;jrenoved j;! Is tart;] final!;I;!;start;!fInal {;!;! 1;I I;I;!;I;!;j;:Wh];I 2.5 I;0.7;I;I;! 0.3;!;0.1;!;! I;! 1;!;!;•;!;!;!C6HC1S !;110 I;5;!;!;I 1.5;1;1.3;j;! 6 5 !;! I;!;!;I;!;i;J CC1 1;500;! 8 1;3;!;97.8;1;500;I 1.3;!;3;!;99,15 I;I t;I I;!;!;!;I;I;! DCBP 1;500;I 6 1;0.2;1;98.8;I;500;I 3;!;0.16;!;99.4 !;! I;1 I;!;!;!;!;I;! PS* I I 0.02! 0.002! I ! 0.1 t 0.008! ! 1 1 1 ! ! J ! ! i - PS: perchlorostyrene - Values in mg 223232

Claims (8)

WHAT WE CLAIM IS:

1. Process for destroying at least one chlorinated organic product containing more than 2 carbon atoms, which comprises placing the product in contact with at least one liquid chloroaluminate (as hereinbefore defined) at a temperature not exceeding 300° C, the quantity of chlorinated organic product being less than 5,000 ppm of the chloroaluminate.

2. Process according to claim 1 in which the chloroaluminate is sodium chloroaluminate.

3. Process according to claim 2 in which the sodium chloroaluminate contains at least 50 mol% of aluminium chloride.

4. Process according to any one of claims 1 to 3 in which the said temperature is from 200° to 300° C.

5. Process according to any one of claims 1 to 4 in which the chloroaluminate contains at least one reducing metal powder.

6. Process according to claim 5 in which the reducing metal is aluminium.

7. Process according to claim 5 or 6 in which the mean particle size of the powder does not exceed 500 (i.

8. Process according to claim 1 substantially as described in any one of the Examples. „ , By MMHer/Their Authorised Agerifei A. J. PARK & SON