Chemically complex bio-oils from biomass fast pyrolysis are promising intermediate renewable energy carriers, which can be transformed into hydrogen (H-2) or alkanes (C-1-C-6) by aqueous-phase processing. Bio-oil transformation can be accomplished in three steps: water extraction, low temperature hydrogenation of the water-soluble portion, and aqueous-phase reformation (to H-2) or dehydration/hydrogenation (to alkanes). In this work, the reaction kinetics of mild aqueous-phase hydrogenation (T <= 423 K) of four model compounds of the bio-oil aqueous fraction, viz. hydroxyacetone, hydroxyacetaldehyde, guaiacol and 2-furanone was studied in a slurry reactor using Ru/C catalyst. The investigated compounds were converted to 1,2-propanediol, ethylene glycol, 1,2-cyclohexanediol and gamma-butyrolactone, respectively. Wide ranges of temperature (323-423 K), H-2 partial pressure (0.69-2.76 MPa) and catalyst loading (0.2-2 kg/m(3)) were examined. To deduce the mechanistic features of reaction kinetics, Langmuir-Hinshelwood-Hougen-Watson (LHHW) type models were considered. (C) 2012 Elsevier B.V. All rights reserved.