New insights into the mechanism of sorbitol transformation over an original bifunctional catalytic system

Sorbitol can be selectively transformed into liquid alkanes over a bifunctional catalytic system Pt/ZrO2 + TiO2-WOx. 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. (C) 2014 Elsevier Inc. All rights reserved.