CONICET | Buscador de Institutos y Recursos Humanos

The gas-phase upgrading of 2-hexanol, a model molecule of the primary conversion of sugars, towardhigher molecular weight compounds of application as liquid transportation fuels was investigated onCu?MI?MIImixed oxides (MI, MII: Mg2+, Al3+, Ce4+) at 573 K and 101.3 kPa. Catalysts were prepared bycoprecipitation and characterized by several techniques such as BET surface area, XRD, TPD of CO2andNH3, TPR and N2O decomposition. The bifunctional metal?base catalytic process occurs through a series ofsequential steps comprising dehydrogenation, C C coupling, dehydration and hydrogenation reactions.Nano-sized Cu0particles promote dehydrogenation and hydrogenation steps whereas acid?base sitesprovided by MI(MII)?O pairs participate in the C C coupling reaction. In general, main products wereC9?C12 compounds that represented ¡60% of the product pool. Branched C9?C24 compounds such asketones, alcohols and alkanes were obtained with yields of up to 91% on a Cu?Mg?Al mixed oxide with8 wt.% Cu (catalyst 8.0CuMgAl). This catalyst presented well dispersed Cu0particles and a high numberof base sites with moderate basic properties as well as a low number of acid sites. The rate-limiting stepof the bifunctional process leading to C9?C24 products on catalyst 8.0CuMgAl was the metal-promotedhydrogenation step, but the reaction can be controlled by the C C bond formation step on less basiccatalysts. By carrying out experiments under different reaction atmospheres (N2or H2) and at differentcontact times, a reaction pathway leading to formation of odd carbon atom number products (C9, C15and C21) is postulated in contrast to the conventional aldol condensation pathway toward even carbonatom number products (C12, C18 and C24). The former prevails under conditions at which the catalystsurface is deprived of hydrogen atoms. DOI: 10.1016/j.apcata.2015.01.010