Measurement and correlation of liquid-liquid equilibria for cyclohexane-heptane-N,N- dimethylformamide ternary system

Liquid-liquid equilibrium( LLE) data were measured for ternary system( n-heptane-cyclohexane-N,Ndimethylformamide) at atmospheric pressure and different temperatures( 30,40,50 ℃). The experimental data were correlated using the Bachman and the Othmer-Tobias correlation,and the results showed a good correlation.Complete phase diagrams were obtained by tie-line data and determining solubility. The universal quasichemical activity coefficient( UNIQUAC) and the non-random two-liquid equation( NRTL) were used to predict the phase equilibrium in the system by the interaction parameters from the experimental data. It shows that UNIQUAC and NRTL used for LLE can provide a good correlation. The separation factors,distribution coefficients and selectivity were obtained according to the experimental data.