Résumé
Pt/C catalysts were prepared by impregnation of carbon xerogels with H2PtCl6 aqueous solutions. Three supports with various pore textures were used: two micro-mesoporous (maximum pore size = 10 and 40 nm, respectively) and one micro-macroporous (maximum pore size = 70 nm). After impregnation, drying and reduction, the metal particles were at most 1–1.5 nm in diameter. The Pt dispersion was close to 100% in the case of the xerogel with large mesopores. For the two other supports, a small fraction of Pt was trapped in blocked micropores. The specific catalytic activity obtained for benzene hydrogenation was 4–10 times higher than that obtained with active charcoal-supported catalysts prepared by a similar method. The high dispersion of Pt was attributed to the presence in the xerogel of large mesopore or macropore volumes, which facilitates impregnation, and a low amount of oxygenated surface groups.