Phase Behaviors of Water + Acetic Acid + Methyl Acetate + p-Xylene Mixture at 101.32 kPa

Abstract

In this study, the experimental results exhibit that the mixture of water + acetic acid + methyl acetate + p- xylene has interesting phase behaviors of vapor-liquid equilibrium (VLE) and vapor-liquid-liquid equilibrium (VLLE) under pressure of 101.32 kPa. The VLE and VLLE data were obtained with a condensed-vapor-phase-recirculating still as described in the text. The experimental data are useful to the design and operation of the purification process of acetic acid. The experimental VLE and VLLE data were then correlated with the NRTL and the UNIQUAC activity coefficient mod- els, respectively, as described in the text. Attributed to the presence of acetic acid, which is a strong polar component, the association effect of molecules of this component in the vapor phase was considered and handled with the approach of Hayden and O'Connell for correlation. production, will form a p-xylene-water azeotrope with water content larger than the azetropes of water-ethyl acetate, wa- ter-propyl acetate, water-isobutyl acetate, and water-butyl acetate. The advantage of the large water content and that of p-xylene is a by-product of reaction causes it to be consid- ered as one of the feasible entrainer. To study the feasibility of using p-xylene as an entrainer, the thermodynamic data of the quaternary mixture of water + acetic acid + methyl ace- tate + p-xylene are necessary. Unfortunately, the phase equilibria of this mixture have not been reported in the litera- ture. In this study, the phase behaviors of vapor-liquid equi- librium (VLE) and vapor-liquid-liquid equilibrium (VLLE) were observed and the experimental data of phase equilib- rium of this quaternary mixture useful for process design were provided. Then the experimental VLE and VLLE data were correlated with the non-random two liquid (NRTL) and the universal quasi-chemical (UNIQUAC) activity coeffi- cient models, respectively, as discussed in the latter part of this report.