Study On Phase Equilibria Of P-Xylene-Acetic Acid-Water-n-Propyl Acetate-Methyl Acetate System

The accurate and complete phase equilibria data, as well as reliable theoretical models and parameters accordingly, are significant for process simulation and parameters optimization. During the production process of PTA, in order to improve separating effect of acetic acid solvent dehydration column, phase equilibria of p-xylene-acetic acid-water-n-propyl acetate-methyl acetate system have been researcded herein based on the field condition of a chemical plant that n-propyl acetate was used as entrainer.Isobaric vapor-liquid equilibria of four sets of binary mixtures of acetic acid-p-xylene, n-propyl acetate-methyl acetate, methyl acetate-p-xylene, n-propyl acetate-p-xylene and four sets of ternary systems of acetic acid-n-propyl acetate-methyl acetate, methyl acetate-p-xylene-acetic acid, n-propyl acetate-p-xylene-acetic acid, methyl acetate-n-propyl acetate-p-xylene have been measured respectively at 101.33kPa using Ellis ebulliometer.The four sets of binary experimental data, in combination with literature VLE data of other binary systems, have been correlated by Fortran program developed independently by our team. To take into account of association effect of acetic acid in the vapor phase, Hayden O'Connell method has been considered. Each binary VLE data have been correlated by NRTL and UNIQUAC models respectively. It was found that both NRTL and UNIQUAC models could satisfactorily correlate these VLE data of binary system. The obtained model parameters have been used further to predict VLE data of ternary systems subsequently. The equilibria values obtained in this way agreed well with the experimental values.To verify the reliability of current interacting parameters in ASPEN PLUS database, all VLE and LLE data utilized from experiments and literatures have been correlated by this software directly. Ten sets of binary parameters have been obtained in this way accordingly. Good agreement is observed between correlated and calculated results, which were obtained by correlated and original parameters respectively. For azeotropic mixtures, the azeotropic point and composition calculated by two methods agree with each other very well, proving that the parameters obtained herein meet the engineering requirements.