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

Isobaric vapor-liquid equilibrium (VLE) data for formic acid-water, formic acid-pentyl formate and formic acid-water-pentyl formate systems were measured at 101.325 kPa by using an improved Rose still. The association effect of formic acid in vapor phase was considered, and the nonideality of vapor phase was corrected by Hayden-O'connell equations. The VLE data for formic acid-water and formic acid-pentyl formate systems were correlated by the NRTL and UNIQUAC models, and the binary interaction parameters of these models were obtained by applying the nonlinear least square method. Combining the obtained NRTL model parameters of binary systems with partial ternary VLE data, the NRTL model parameters of water-pentyl formate system were determined, and then the obtained NRTL model parameters were used to predict the VLE data of the ternary system. For ternary system of formic acid-water-pentyl formate, the average absolute deviations of predictions for vapor-phase mole fraction of water and pentyl formate are 0.0292 and 0.0273, respectively, and for the equilibrium temperature is 0.94°C.