States of Pt in Pt/C catalyst precursors after impregnation, drying and reduction steps

The characterization of Pt/C catalysts after impregnation and activation 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, The catalysts were prepared from a purified peach pit derived carbon and two H(2)O(2)-functionalized supports obtained from it. Results showed that the interaction of H(2)PtCl(6) with the carbon implies a redox process in which after impregnation and drying steps, the metal complex is stabilized as Pt(2+) 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 CO(2) desorbed from the carbon surface, take place. It was also found that the Pt(2+) species are reduced to zerovalent Pt even by thermal treatment of the dried samples with He. The electronic state of reduced platinum is not modified by the differences in the support surface chemistry. (C) 1998 Elsevier Science B.V.