Simulation and related experimental validation of acetic acid/water distillation using p-xylene as entrainer

The separation of water/acetic acid mixtures by conventional distillation is not suitable for industrial applications. With reference to terephthalic acid production, we selected p-xylene as an entrainer to run an azeotropic distillation, being the principal raw material of the process. The phase equilibria of the binary and ternary systems are discussed, and the UNIQUAC activity coefficient model was adopted for the simulations. A robust nonlinear regression of the UNIQUAC binary interaction parameters was performed with the BzzMath optimizer on the basis of the literature equilibrium data. Using a batch and a micropilot distillation column, 5 m height and 15 trays, run in different operative configurations, the feasibility of the process was demonstrated. In addition, the experimental data were compared with the simulations obtained with the SimSci PRO/II process simulation software. An overall tray efficiency of 0.53 was estimated and adopted in all simulations. The separation results confirmed that p-xylene is a suitable entrainer to separate acetic acid/water mixtures.