Formation of PCDFs during chlorination and oxidation of chlorobenzene in chlorine/oxygen mixtures around 340 °C

Homogeneous gas-phase chlorination of chlorobenzene in the presence of oxygen at 330–350°C gives substantial amounts of PCDFs, up to 6% on the major product, the dichlorobenzenes.Chlorine atoms abstract H from chlorobenzene, the resulting chlorophenyl radicals reacting rapidly with Cl2, or with O2. The latter reaction leads to chlorophenoxyl radicals. Part of these appear to be further chlorinated before condensation occurs to mainly D2CDF, T3CDF and T4CDF. The simultaneous production of CO and (extra) HCl shows that (chlorine initiated) slow combustion also takes place, presumably by reaction of chlorinated phenylperoxyl- and/or phenoxyl radicals with oxygen.