Highly active Pd-on-magnetite nanocatalysts for aqueous phase hydrodechlorination reactions.

Nanoscale catalyst particles are already in focus as excellent tools in catalytic processes and intensive research is currently optimizing their performance. As known from nanosized metal particles, nanocatalysts have the potential of very high reaction rates due to their high specific surface areas and low mass transfer restrictions. In this study, we generated extremely active palladium catalysts on the basis of colloidal magnetic carriers. The most active catalyst contains only traces of Pd (0.15 wt %) on nanomagnetite as carrier. Pd-on-magnetite was successfully tested in batch experiments for the hydrodechlorination (HDC) of the chlorohydrocarbons trichloroethene (TCE) and chlorobenzene. For the HDC of TCE, second-order rate coefficients of approximately 1.6 x 10(4) L g(-1) min(-1) were measured. Such high activities have never been described before for Pd-containing catalysts in aqueous phase HDC reactions. The ferrimagnetism of the carrier enables a separation of the nanocatalyst from the treated water by means of magnetic separation. This allows the catalyst to be reused several times, which is an important advantage compared to other nanoscale catalytic systems such as pure Pd or Pd-on-Au colloids.