Solid-liquid, liquid-liquid and vapour-liquid equilibrium measurements for binary and ternary systems containing building blocks of biomass origin such as propionic acid, lactic acid and alternative solvents like carbon dioxide and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid have been carried out at 313.15K The binary solid-liquid and liquid-liquid equilibrium measurements were performed at ambient pressure The vapour-liquid equilibrium was studied in the range of pressure from 3 54 to 12 MPa while ternary systems were examined at 9,10 and 12 MPa The samples from the coexisting phases were taken and the compositions of both liquid and vapour phases were determined experimentally. The three-phase system was observed for lactic acid + ionic liquid + CO2 as well. The achieved results were correlated using the Peng-Robinson equation of state with the Mathias-Klotz-Prausnitz mixing rule The set of interaction parameters for the employed equations of state and the mixing rule for the investigated systems were obtained (C) 2010 Elsevier B V. All rights reserved.