Isobaric vapor-liquid equilibrium(VLE)data were measured for binary mixtures of toluene+N-formylmorpholine,toluene+3-methylthiophene and 3-methylthiophene+N-formylmorpholine at 101.33 kPa.The VLE data of the binary systems were found to be thermodynamically consistent.The saturated vapor pressure calculated by CSGC-PR equation of the pure component had higher accuracy than that calculated by Antoine equation.The liquidphase activity coefficients of the binary systems were calculated by the Wilson,NRTL and UNIFAC models,and the binary interaction parameters of the three models were determined by the VLE data.The Wilson model was selected as the most suitable model to predict the VLE data of the ternary system of toluene+3-methylthiophene+N-formylmorpholine,The relative volatility between toluene and 3-methylthiophene was also calculated.Moreover,the effect of N-formylmorpholine as solvent was studied.When the molar ratio of solvent to feed(S/F)was 7,the relative volatility reached 1.904,which is almost twice the relative volatility without solvent.Therefore,N-formylmorpholine can be considered as an effective extracting agent for the separation of the close-boiling mixture of toluene+3-methylthiophene by extractive distillation.