Dechlorination of dioxins with supported palladium catalysts in 2-propanol solution

Dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (co-PCBs) was carried out in a solution of NaOH in 2-propanol in the presence of Pd/C and Pd/Al2O3. The dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD) proceeded completely with Pd/Al2O3 at 35 degreesC to give a chlorine-free product, dibenzo-p-dioxin (1313). In contrast, the reaction catalyzed by Pd/C under the same conditions was not complete: unreacted substrate and partially dechlorinated products remained on the catalyst. When PCDD/Fs and co-PCBs collected from a commercial solid-waste incinerator were dechlorinated by means of this catalytic system at 82 degreesC, Pd/Al2O3 exhibited excellent activity, and the concentrations of toxic congeners decreased nearly to the experimentally detectable limits. (C) 2004 Elsevier B.V. All rights reserved.