Long-range catalytic hydrodechlorination of preadsorbed DDT at ambient temperature

Reductive catalytic conversion of DDT (p,p′-dichlorodiphenyltrichloroethane) was studied under ambient conditions in a hydrogen atmosphere using platinum and palladium deposited on several supports, in particular on porous alumina and silica. Almost complete hydrodechlorination and hydrogenation of DDT and its dehydrochlorination byproduct DDE (p,p′-dichlorodiphenyldichloroethene), leading to the formation of diphenylethane (with Pd) and dicyclohexylethane (with Pt), were observed at ambient temperature within minutes or hours. Rapid hydrodechlorination also takes place after depositing DDT and the metal component on separate particles and mixing them mechanically. This long-range reactivity can be explained either by a fast surface diffusion of DDT or DDE, or by hydrogen spillover. Irrespective of the mechanism, the reactivity thus bridges the barrier across solid particle interfaces. Most findings indicate the fast diffusion of target compounds as dominant mechanism for the observed long-range reactivity.