Application of the conduct-like screening models for real solvent and segment activity coefficient for the predictions of partition coefficients and vapor-liquid and liquid-liquid equilibria of Bio-oil-related mixtures

The 1-octanol/water partition coefficients (log P) at 298.15 K and the vapor-liquid and liquid-liquid equilibria (VLE and LLE) of biofuel-related mixtures have been predicted with four different thermodynamic models: conduct-like screening models for real solvent (COSMO-RS), conduct-like screening models for segment activity coefficient (COSMO-SAC) (2002 version), modified COSMO-SAC (2006 version), and universal functional activity coefficient (UNIFAC). The 2002 version of COSMO-SAC gives more reasonable predictions for log P for most investigated mixtures than the other two approaches when appropriate molecular geometries are chosen for the computation of the σ profiles. However, the COSMO-RS model gives better predictions for VLE pressures and vapor-phase compositions for biofuel-related mixtures, as well as for the LLE of the 1-octanol + water and furfural + water mixtures. The accuracy of the models for the predictions of the partition coefficients and VLE may be improved by changing the molecular conformations used to generate the σ profiles. Generally, the three COSMO-based models give better predictions than UNIFAC for log P and VLE of the investigated systems and can be applied to predict the thermodynamic properties of the biofuel-related mixtures especially when no experimental data are available.