Modeling systems relevant to the biodiesel production using the CPA equation of state

In this study, CPA parameters for heavy esters, glycerides, organic acids, and glycerol are presented, together with trends of these parameters against the van der Waals volume. Such trends allow the prediction of parameters for compounds for which data are not available. Pure fluid parameters were estimated by adjusting model predictions to recent DIPPR correlations and carefully selected literature data. Then, the performance of CPA was evaluated in correlating the vapor – liquid and liquid – liquid equilibrium of binary systems containing fatty acids and their esters, glycerides, water, alcohols and/or glycerol. Satisfactory correlation results were obtained using one (water-acids, alcohols/water - glycerol) or two (systems containing fatty acid esters with water, alcohols or glycerol and mixtures containing glycerides and alcohols) interaction parameters. Moreover, the interaction parameters show smooth trends with carbon chain length, permitting extrapolation for systems for which data are not available. Finally, the estimated parameters and correlations were used for the prediction of liquid-liquid equilibrium of one ternary and one multicomponent mixture. The results showed that accurate predictions are feasible, however indicated the need of more accurate data, at least for important binary mixtures, such as the systems with glycerol.