Geometric Structures of Associating Component Optimized toward Correlation and Prediction of Isobaric Vapor–Liquid Equilibria for Binary and Ternary Mixtures of Ethanal, Ethanol, and Ethanoic Acid

Abstract

It has relatively been difficult to accurately correlate and predict vapor–liquid equilibrium (VLE) data for the strongly associating system containing the carboxyl acid due to its monomer undergoing partial dimerization and even higher polymerization in the vapor and liquid phases. Herein, this paper reports that the formation state for the associating component mainly has been the existence of dimer in the vapor and liquid phases through the geometric structures of ethanoic acid investigated theoretically with density functional theory (DFT), and the VLE data for the associating ternary system ethanal + ethanol + ethanoic acid and the three constituent binary systems were measured using a recirculating still at 101.325 kPa. Marek’s chemical theory was considered due to the associating species as the dimer existence in the both phases. The three experimental binary data sets were independently correlated using nonrandom two-liquid (NRTL), Wilson, and universal quasichemical activity coefficient (UNIQUAC) model, respectively, and the binary parameters were applied to predict the VLE data for ternary system without any additional adjustment. By comparison with the measured values, the ternary equilibrium values predicted agreed well with the measured values in this way. The thermodynamic consistency of the experimental VLE data was checked out by means of the Wisniak’s L–W test for the binary systems and the Wisniak–Tamir’s modification of McDermott–Ellis test for the ternary system, respectively.