TPD AND TPR CHARACTERIZATION OF CARBONACEOUS SUPPORTS AND PT C CATALYSTS/

Temperature Programmed Techniques have been applied to the characteriz ation of carbonaceous supports with different surface chemistry and th e platinum catalysts prepared with them. Five different supports are o btained from a phenolformaldehyde char submitted to several treatments consisting of oxidation and selective removal of surface oxygen compl exes and addition of calcium. Platinum was loaded on the supports by i mpregnation with aqueous solution of two different precursors: H2PtCl6 and [Pt(NH3)4]Cl2. TPD experiments provide valuable information about the surface chemistry of supports (oxidation degree, nature, and stab ility of the oxygen groups formed). TPR experiments allow us to analyz e their behaviour under reduction conditions. TPR profiles of the supp orts show the reaction with the nascent sites formed after oxygen comp lexes' decomposition. Pt/C catalysts were also studied by TPR in order to analyze the reduction process of the active phase in relation to t he surface characteristics of the support and the nature of the platin um precursor. It has been observed that the surface chemistry of the s upports strongly affects the precursor/support interaction and, hence, the behaviour of the platinum species during their reduction. Further more, an important spillover of hydrogen to the support is observed at relatively low temperature, which overlaps with the precursor reducti on process.