Bio-oil upgrading over platinum catalysts using in situ generated hydrogen

The liquid phase upgrading of a model bio-oil was studied over a series of supported Pt catalysts. Pt/Al₂O₃ showed the highest activity for deoxygenation, the oxygen content of the model oil decreasing from an initial value of 41.4 wt% to 2.8 wt% after upgrading. GC-MS analysis of the oil showed it to be highly aromatic, the major components corresponding to alkyl-substituted benzenes and cyclohexanes. CO₂ was formed as the major gaseous product, together with lower yields of H₂ and C₁-C₆ hydrocarbons. Based on the product distribution, a reaction scheme is proposed in which light oxygenates predominantly undergo reforming to CO₂ and H₂, with C-O bond breaking/hydrogenation (to afford alkanes) as a minor pathway. In a parallel process, aromatics undergo C-O cleavage/hydrogenation, affording benzenes and cyclohexanes. The highly alkylated nature of the products appears to be a consequence of the acidic nature of the reaction medium, favoring the occurrence of aromatic electrophilic substitution reactions.