Study on isobaric vapor-liquid equilibrium of formic acid-water-n-butyl formate systems

Isobaric vapor-liquid equilibrium (VLE) data of the systems of formic acid-water, formic acid-butyl formate and formic acid-water-butyl formate were measured at 101.33 kPa by using an improved Rose equilibria cell. The association and nonideality of formic acid in vapor phase were considered. The nonideality of vapor phase was correlated by Hayden-O' connell equations. VLE data of the systems of formic acid-water and formic acid-butyl formate were correlated by the NRTL model, and the binary interaction parameters were gotten by applying the nonlinear least square method. Combining the obtained model parameters of binary systems with the ternary VLE data, the model parameters of water-butyl formate system were correlated. The model parameters obtained were used to predict ternary VLE data. For ternary system, the average absolute deviations in vapor-phase mole fraction of formic acid and butyl formate were 0.0152 and 0.0184 respectively and that in the equilibrium temperature was 1.20°C, the experimental value basically agrees with the predicted value.