IE60535B1 - Process for destroying at least one chlorinated product containing more than two carbon atoms - 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

ATOCHEM, A FRENCH BODY CORPORATE OF LA DEFENSE 10, 4 & 8 COURS MICHELETf 92800 PUTEAUX, FRANCE.

(C) Copyright 1994,, Government of Ireland» The present invention relates to a process for destroying at least one chlorinated organic product 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 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. 1° Chlorinated organic products, as well as certain pesticides and chlorinated aromatics such as hexachlorobenzene or polychlorobiphenyls (PCS) can give rise to toxic products when they are burnt like an ordinary flammable product® m order to avoid generating toxic products these chlorinated products are destroyed at a high temperature under specific conditions.

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

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

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

A much simpler process for destroying these products, capable of operating below 300°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, characterized in that these products are placed in contact with a bath of at least one chloroaluminate, the initial concentration of chlorinated organic products being less than 5000 ppm.

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 chloroaluminate.

It is also preferred that the sodium chloroaluminate f should contain at least 50 mol% of aluminium chloride and ί should have a melting point below 200 C. * 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 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 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, this solid phase may be poured into the bath of chloroaluminate, preferably stirred. Car® 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 are to be destroyed are in a gaseous phase, either alone or r mixed with light chlorinated products and/or carrier gases» For examplef the gas may be one produced by combustion? consisting of nitrogen containing carbon dioxide, carbon monoxides· chlorinated products and possibly oxygen.

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

It is preferable that th© chlorinated products should be in an anhydrous phase. The gas containing the chlorinated products may be dried by contact with an 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. « 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 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 t them. The residence time may vary within wide limits but is 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., 1θ 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 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 2θ 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 .c C* which are insoluble or which cannot remain in suspension in 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 ja. When metals are employed, the 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 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» 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 metal chloride or chlorides which have been produced may mix 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 inventions EXAMPLE 1 500 g of sodium chloroaluminate in which the mole 10 ratio AlCl^/NaCl = 1 are introduced into an electrically heated 1-1 itre Pyrex round flask fitted with a propeller stirrer rotating at 300 rev/min... The product is heated to 200°C, stirred, and then 02 g of hexachlorobenzene and 0.1 g of decachlorobiphenyl are Introduced. After 1 hour at 200°C, the aolten bath is purged for 15 ainutes with a stream of 50 L/fa of which is washed io a bubbler containing 100 ml of hexane.

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

The results are shown in Table 1.

EXAMPLE 2 The same test is carried sut, but 52 of fine aluminium powder (Pechiney XT 4® grade) are additionally introduced into the chloroaluasinate bath. After 1 hour at 200°C followed by purging with SO l/h of Ng for 15 min,, a sample of the bath and of hexane is taken for quantitative analysis.

TABLE 1 CHLOR- ΙΝΑΤΕΘ © $ © $ © WITHOUT Al s <*> « a WITH if? *** ί 1 αί «> At S' lif » organic f © I a» ® ** Jft, hC - * φ ΐ Si (U 3( SI tt, a PRODUCTS Sf BATH Jhexarse I product 1 ΘΛΤΗ if hexane $ product™ * $ 4 ! * $ removed J Si SI !( w 1 : © start' _ final., φ <*, $ ! start * & ft u © inat; v IB © renewed' © i Si 1 CXI. ! 200 , S 6 · J 1 ί · ,i nil s? 13 2 1 ! I I 37.7 .1 I! 2 1 ! 1 00 123 I 1 1 SI I ώ < 3.5 ! 53.7 ί I ! ί BCBP* ! 100 141.3 1 0,.401 53.3 2! 1 00 1 3·8 ! 0.2 I 96 ! ί Si I W 1 n Si i? i? u © φ © φ I» ® © * BCSPs desachlorsbiphenyt - Values io mg ί. ο IS EXAMPLE 3 Th® operation is carried out in the sane apparatus as employed for Exaaples 1 and 2, but the operating conditions are changed: - bath temperature: 2S0°C - weight of the chloroaluainate bath: SOO g - addition of 51 of AI powder (Pechiney XV 49) - duration of the test: 2 hours - nitrogen purge after 2 hours: IS min - initial, addition of: 500 sag of hexachlorobenzene SOO sag of decachlorobipbenyl The results are given in Table 2.

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

The results are shown in Table 2,., TABLE 2 S Ϊ jCHLOR- ® jlMATEO j 20 j ORGANIC;* auaATIOfi 2 h 0U8«TXON i- h SpaoouCTSS! ©atm ? ί 1 lasers 3 final! Ϊ 3 χ οί » hexane-3 produevS 8aTH '« rsiwowecl j s j > star? Jf'ins, I< _s I 2 Z of ί * hexane.! product» jP®mewed j I ! » 3 J IS 2 1 ! 8 i> ! 2.5 ! 3 0.1 . Ϊ 3 * « 1 2 0.3 2 2 0.1 1 2 ΐ no R! w 3 S ! I rc 1 1.5 Ϊ N 1.3 « : ί SOO 3 a 3 3 j 97 „8 ί SOO 1.3 ! 3 2 99.15 S 3 Ϊ I 9/ « rc i !' 3Ci3? 3 SOO 3 6 % 0.2 98.8 ί SOO 2 3 * 0.16 3 99.4 ί * 3 3 ί I 3 « « ί ; PS* 3 ί 0.023 0.0021 1 2 0.1 i 0.008’ ! ΐ 3 ?1 i 1 5 « ί 2. ! - PS: per chlorostyrene - Values in no

Claims (9)

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 5 liquid chloroaluminate, the initial concentration of chlorinated organic products being less than 5000 ppm.

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

3. Process according to claim 2 in which the sodium 10 chloroaluminate contains at least 50 moll of aluminium chloride.

4. , Process according to any one of claims 1 to 3 in which the temperature of the chloroaluminate does not exceed 30O°C.

5. » Process according to claim 4 in which the said temperature is from 2QQ° to 300°C.

6. , Process according to any one of claims 1 to 5 in which the chloroaluminate contains at least one metal · powder.

7. Process according to claim 6 in which.the metal is aluminium.,

8. », Process according to claim 6 or 7 in which the mean particle size of the powder does not exceed 500 p.

9. . , Precess according to claim 1 substantially as described in ans/ one of the Examples.