Kinetics of Aqueous-Phase Hydrogenation of Levoglucosan over Ru/C Catalyst

Bio-oil from biomass fast pyrolysis can be transformed into hydrogen (H-2) or alkanes (C-1-C-6) by aqueous phase processing (APP). Low temperature hydrogenation of the water-soluble portion of bio-oil is a useful intermediate step of APP. In the present work, the anhydrosugar levoglucosan (LG) was selected as a model compound of the bio-oil aqueous fraction. LG hydrogenation was studied in a slurry reactor using heterogeneous Ru/C catalyst. Kinetic data were obtained experimentally in the range of temperatures, 398 to 433 K, H-2 partial pressures, 0.69 to 2.07 MPa, initial LG concentrations, 0.6 to 3.1 mM and catalyst loading, 0.5 to 1.5 kg/m(3). Langmuir-Hinshelwood-Hougen Watson (LHHW) kinetics was used for modeling initial rates of LG disappearance. Two kinetic models assuming that surface reaction is rate-controlling reasonably represented the kinetic data. Model 1 assumed competitive adsorption of dissociatively chemisorbed H-2 and LG, whereas model 2 was based on competitive adsorption of molecular H-2 and LG. However, model II seemed to be not feasible, because of the low activation energy value and the assumption of reaction with molecular H-2.