GB504569A - Manufacture of benzene hexachloride - Google Patents

Abstract

504,569. Chemical apparatus. GRANT, A. E., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Oct. 26, 1937, No. 29273. [Class 1 (i)] [Also in Group IV] Benzene hexachloride is manufactured by passing cold benzene, e.g. as a film or spray at about 20‹ C. and not above 60‹ C. countercurrent to chlorine while exposing the reactants to actinic radiation, delivering the resulting liquid to a delay or capacity vessel wherein the reaction between the benzene and dissolved chlorine is completed, and thence to a boiler from which unchanged benzene is vaporized and returned after condensation to the reaction zone. Benzene hexachloride can thus only separate in the boiler and cannot block the apparatus. Any substituted benzenes formed or retained in the boiler and heptachlorbenzene or higher chlorinated bodies cannot be formed. Cooling devices may be employed if necessary. The capacity vessel and reaction zone are both illuminated by actinic light. Benzene may run down the inner surface of the reaction tube up which chlorine is passing or may be sprayed into the top of the tube or may descend as a column of liquid into which the chlorine is bubbled. The capacity vessel may be merely a large receiver into the lower part of which liquid is delivered from the reaction zone and from the upper part of which it may be drawn off and delivered to the boiler or a coiled glass tube may be used. The reaction tube may be packed with transparent material to ensure the exposure of a large area of benzene to the chlorine: The process may be worked by continuously or intermittently introducing benzene to the top of the reaction tube, and continuously or intermittently withdrawing liquid from the boiler, removing solid hexachloride therefrom and either returning the mother liquor to the boiler or separately distilling the benzene therefrom and returning it to the reaction tube. In a modification benzene is passed through a U-shaped, apparatus and chlorine introduced into the lower part of the limb down which the benzene is flowing. This limb then corresponds to the reaction zone and the other to the delay vessel, both limbs being illuminated. Metals such as iron or copper which catalyse substitution reactions should not be employed. Specifications 483,823, [Group IV], and 486,298 are referred to.