Dechlorination of hexachlorocyclohexanes with alkaline 2-propanol and a palladium catalyst.

Hexachlorocyclohexane isomers (alpha-, beta-, gamma- and delta-HCH) were dechlorinated in 2-propanol by means of stoichiometric reaction with NaOH and subsequent catalytic dechlorination over a supported palladium catalyst (Pd/C). When the HCH isomers (2-10 mmol/l) were reacted with a molar excess of NaOH ([NaOH]/[HCH]>9) in 2-propanol, transformation of alpha-, gamma- and delta-HCH to trichlorobenzenes (TCBs) was complete within 5 min at room temperature, but beta-HCH was less reactive. Analysis of TCB isomers produced from individual HCH isomers showed that 1,2,4-TCB was always predominant (70-90% of the product) and 1,2,3-TCB and 1,3,5-TCB were minor products.

Dechlorination of polychlorinated dibenzo-p-dioxins catalyzed by noble metal catalysts under mild conditions.

Dechlorination of polychlorinated dibenzo-p-dioxins such as 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) and 1,2,6,7-tetrachlorodibenzo-p-dioxin (1,2,6,7-TCDD) was carried out in a solution of NaOH in 2-propanol in the presence of carbon-supported noble metal catalyst (Pd/C or Rh-Pt/C) at temperatures between 23 and 35 degrees C. At initial concentrations of 140-240 micrograms/ml, 2,7-DCDD and 1,2,6,7-TCDD were efficiently converted to a chlorine-free product, dibenzo-p-dioxin (DD), in high yield (60-80%). The conversion of 2,7-DCDD and 1,2,6,7-TCDD and the yield of DD were hardly affected by the atmosphere (N2 or air).