Hydrogenolysis of organohalogen compounds over palladium supported catalysts

Catalytic hydrodehalogenation is one of the most promising methods for detoxification of organohalogen waste. A variety of catalytic systems has been used, although palladium catalysts are the best choice because of their optimal catalytic properties, Catalytic hydrodehalogenation on palladium catalysts is carried out in both the liquid and gas-phases. The experimental procedures for the catalytic hydrodehalogenation are reviewed; the hydrogen source can be either molecular hydrogen or a hydrogen donor in the so called hydrogen-transfer hydrogenolysis. A wide variety of hydrogen donors has been used, including inorganic salts (phosphinates) organic salts (formates), alcohols, proaromatic compounds, etc. Kinetics and mechanisms proposed for hydrodehalogenation are presented, and both agreements and disagreements on the mechanistic aspects are discussed. Catalysts modification (base addition, support modification, second metal addition, etc.) as well as its transformation during the hydrogenolytic process (i.e. deactivation) are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.