New bifunctional catalytic systems for sorbitol transformation into biofuels

Tungstated oxides were prepared from several supports and characterized. The tungsten surface repartition and availability depends on the initial support. The acidity in water was evaluated through a model compound reaction, cyclohexanol dehydration. The results show that acidity in water is completely different from gas phase acidity (from NH3-TPD), evidencing the crucial role of water in the acid catalytic activity. The tungstated oxides were then mixed with Pt/ZrO2 to obtain a bifunctional catalytic system, which was used for transforming sorbitol in water. The activity and selectivity is highly dependent on the acid phase. TiO2-WOx led to increased activity and higher selectivity for long chain hydrocarbons (C5-C6 alkanes) which can be valorized as biofuels, when compared to traditional sorbitol transformation catalyst. Al2O3-WOx is not acid in water but produces short alcohols by C-C cleavage. These results provide an incentive for further catalysts preparation. (c) 2013 Elsevier B.V. All rights reserved.