Theoretically and Experimentally Exploring the Isobaric Vapor–Liquid Associating Behavior for Binary and Ternary Mixtures Containing Methanol, Water, and Ethanoic Acid

It is a formidable dilemma for vapor–liquid equilibrium (VLE) association behavior in chemical separation procedures to correlate and predict binary and ternary mixtures containing associated components, since the form of components is completely unknown, such as monomers, homogeneous or heterogeneous dimers, trimers, and even polymers, and so on. Herein, the VLE data for the binary and ternary mixtures, including methanol, water, and ethanoic acid, were measured via the various liquid- and vapor-phase compositions using a Fisher ebulliometer at 101.33 kPa. The geometric configurations and distributions of diverse clusters in methanol, water, and ethanoic acid systems were wholly optimized at the B3LYP/6-31+G­(d) level of theory using Gaussian 09. Then, we established a strategy for computing the liquid activity coefficients by pondering the various association species in the associating system. The approach is named the discrete clusters (DC) model, and the comparison is also provided between the calculating results for the binary systems of the DC model and the UNIQUAC, NRTL, and Wilson models. Moreover, the ternary system’s phase behavior was investigated by using the DC, UNIQUAC, NRTL, and Wilson models without further adjusting model parameters. The DC model conveyed the number of various clusters, indicating better consistency and a smaller deviation from the measured data. These VLE data originating from the DC model can be applied to the design and simulation of the chemical separation process of the binary and ternary association systems.