STATES OF PT IN PT C CATALYST PRECURSORS AFTER IMPREGNATION, DRYING AND REDUCTION STEPS/

The characterization of Pt/C catalysts after impregnation and activati on steps has been carried out by using different techniques: TPD; TPR; XPS; EXAFS and H-2 chemisorption. Furthermore, the catalytic activity of the samples has been tested in the cyclohexane dehydrogenation, Th e catalysts were prepared from a purified peach pit derived carbon and two H2O2-functionalized supports obtained from it. Results showed tha t the interaction of H2PtCl6 with the carbon implies a redox process i n which after impregnation and drying steps, the metal complex is stab ilized as Pt2+ on the carbon surface, The functionalization treatment seems to have no effect on the resulting state of platinum. During the activation step (thermal treatment in H-2), apart from the reduction of Pt species to Pt-0, catalyzed and non-catalyzed reactions involving CO and CO2 desorbed from the carbon surface, take place. It was also found that the Pt2+ species are reduced to zerovalent Pt even by therm al treatment of the dried samples with He. The electronic state of red uced platinum is not modified by the differences in the support surfac e chemistry. (C) 1998 Elsevier Science B.V.