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Sorbitol can be selectively transformed into liquid alkanes over a bifunctional catalytic system Pt/ZrO 2 + TiO 2 –WO x . In this paper, we investigated the reaction mechanism by carefully analyzing the numerous products issued from sorbitol and by studying the reactivity of some identified intermediates (1-hexanol 2-hexanol, 2-hexanone, 2,5-dimethyltetrahydrofuran, 1,2-hexanediol and 1,2,6-hexanetriol). This led us to propose that C C cleavage reactions occur on terminal C C bonds and mainly consist of dehydrogenation–decarbonylation reactions. The limiting steps of the sorbitol transformation are the isosorbide and mono-oxygenated intermediate transformations, especially the hydrogenation of ketones. It is also assessed that diols or triols with n carbon atoms are mainly converted in compounds with n − 1 carbon atoms. Short compounds (1 to 3 carbon atoms) are obtained via a dehydrogenation-retro-aldol reaction pathway and not from isosorbide conversion. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]