GB378866A - Improvements in or relating to the production of chlorinated derivatives of toluene - Google Patents

Abstract

Chlorinated derivatives of toluene are manufactured by passing a mixture of chlorine and toluene vapour through a reaction zone at 250-600 DEG C., the speed of passage being adjusted in such a manner as to increase from a low space velocity of the order of 2-5 reciprocal minutes at the lower end of the temperature range, i.e. 250-350 DEG C., to a high space velocity of the order of 500-2000 reciprocal minutes at the upper end of the range, i.e. 500-600 DEG C. The permissible amount of chlorine in relation to toluene depends upon the temperature, and at temperatures of 400-600 DEG C. the initial amount of chlorine should not exceed half that of toluene vapour, otherwise the mixture may inflame. The parts of the reaction chamber coming into contact with the hot gases are preferably made of non-metallic material such as glass, silica or firebrick. The reaction zone may be packed with inert material such as pieces of silica. The products consist almost entirely of side-chain chlorinated compounds of toluene, but if desired products chlorinated in the nucleus may be obtained by performing the reaction in the presence of chlorine carriers such as iodine or ferric chloride. In an example, a mixture of one volume of chlorine and 2,2 volumes of toluene vapour is passed through a porcelain tube at 510 DEG C. with a space velocity of 520 reciprocal minutes or at 600 DEG C. and 1000 reciprocal minutes, yielding a mixture of benzyl and benzal chlorides. If the quantity of chlorine is increased, e.g. one volume of chlorine to 1,2 volumes of toluene vapour, treated at 250 DEG C., or a mixture of 1,3 volumes of chlorine and one volume of toluene vapour, at 300 DEG C., the percentage conversion of toluene is increased but the proportion of benzal chloride in the product is larger. If a mixture of one volume of chlorine and 2,2 volumes of toluene vapour, containing 1 per cent, by weight of the toluene, of iodine, is passed at 500 DEG C. and 500 reciprocal minutes, a mixture of benzyl and benzal chlorides and chlortoluenes is obtained.