Hydrolysis and Oxidation of Hexachlorocylclohexane in Sub- and Supercritical Water

Commonly used thermal disposal methods for halogenated hydrocarbons like the incineration have the disadvantage that high amounts of toxic and / or corrosive reaction products (HCI, C12 and dioxines) are produced which imply large-scale flue gas collection. Therefore alternative disposal techniques are highly required. In this paper the disposal of gamma-hexachlorocyclohexane (gamma-HCH) under alkaline conditions in normal and supercritical water is presented. The batch-experiments were carried out in an autoclave made of a highly heat resistant NiCrMo-steal. The reaction products in the gaseous, liqiud and solid phase were analysed by chromatographic and spectroscopic methods. Reaction temperatures were varied between 150 and 450 degree Celsius. The ratio of HCH to NaOH was 1:1 or 1:2. Under normal water conditions (up to 300 degree Celsius the conversion of HCH to ionic chloride reaches amounts of 50 % Cl. The remaining Cl-content is found in an organic phase consisting mainly of tri chlorobenzene isomeres. Near and above the critical temperature / critical point of water the conversion of HCH to ionic chloride increases drastically. Conversion rates of bigger than 97 % are reached. Also the hydrocarbon framework is destructed under these conditions, mainly to watersoluble hydrocarbons (25 to 65 %C) and in smaller amounts to gaseous products (up to 5 %C as C02 and CHn).