Study of Pt-CeO2 interaction and the effect in the selective hydrodechlorination of trichloroethylene

The feasibility of a catalytic technology to remediate waste streams of halogenated compounds has been improved in order to increase the selectivity towards valuable compounds. Two series of Pt/CeO2 catalysts prepared by different synthesis protocol, co-combustion and impregnation, have been tested in hydrodechlorination of trichloroethylene in gas phase at mild reaction conditions (temperature between 100 and 300 degrees C, and 1 bar of pressure). The catalytic behaviour of Pt-Al2O3 catalysts was also studied for comparison. Several techniques (BET, XRD, FTIR, HRTEM, etc.) were performed for catalysts characterization. Using the combustion method, the platinum is introduced into ceria matrix, whereas by the impregnation one, the platinum particles are deposited on the surface. In both cases a strong interaction between the support and the platinum particles is observed. Smaller platinum particles sizes are obtained using the impregnation method when compared with the combustion one. When the main product for Pt-Al2O3 catalysts was ethane, the use of CeO2 as support increased the ethylene selectivity. Platinum catalysts obtained by combustion method showed the highest selectivity to ethylene. These results indicate that both the presence of CeO2 as support and the interaction between ceria and platinum play an important role in the selectivity to ethylene. (C) 2008 Elsevier B.V. All rights reserved.