Calculation of complex phase equilibria of DMF/alkane and acetonitrile/alkane systems using a modified Peng-Robinson EoS and the Huron-Vidal mixing rules

Equilibrium and molar volume data are necessary for simulation, sizing and design of chemical process. Simple generalized models that predict liquid-liquid equilibria in wide temperature and pressure ranges are scarce. A modified Peng-Robinson equation of state with Huron-Vidal-NRTL mixing rules is used to calculate phase equilibria and liquid molar volume data for several DMF/alkane and acetonitrile/alkane systems. These systems show a complex phase behavior. The vapor–liquid, liquid–liquid, vapor–liquid–liquid equilibria and liquid molar volumes of DMF/alkane and acetonitrile/alkane systems with alkanes from C4 to C16 were studied. Linear expressions for the binary interaction parameters as function of alkane RT_c/P_c was used to model the experimental data. These expressions were determined only by using experimental liquid–liquid equilibria data of DMF/alkane and acetonitrile/alkane systems. Using those, the modified Peng-Robinson equation of state with Huron-Vidal-NRTL mixing rules offers very satisfying results for the prediction of the phase behavior and liquid molar volume for the studied systems. The equilibrium results are like those obtained with a more intricate model like PCP-SAFT equation of state.