Saturated vapor pressure of 4-fluorophthalic anhydride and 4-chlorophthalic anhydride and isobaric vapor–liquid phase equilibrium of 4-fluorophthalic anhydride + 4-chlorophthalic anhydride: Measurement and modeling

• The saturated vapor pressures for 4-fluorophthalic anhydride and 4-chlorophthalic anhydride were measured.
• The isobaric VLE data were obtained for the 4-fluorophthalic anhydride + 4-chlorophthalic anhydride system.
• The experimental VLE data were correlated by Wilson model, NRTL model and UNIQUAC model.

The saturated vapor pressures of 4-fluorophthalic anhydride and 4-chlorophthalic anhydride at various temperatures ranging from T = (426 to 560) K, and the isobaric vapor–liquid phase equilibrium data for binary system of 4-fluorophthalic anhydride (1) + 4-chlorophthalic anhydride (2) at pressures of 21.33 kPa, 41.33 kPa, 61.33 kPa and 81.33 kPa were measured experimentally by means of an inclined ebulliometer. The relationship between saturated vapor pressure and temperature was fitted by using two Antoine equations and the Antoine constants were acquired for 4-fluorophthalic anhydride and 4-chlorophthalic anhydride, respectively. The semi-empirical method, Herington method was employed to test thermodynamic consistency of the vapor–liquid equilibrium data. The isobaric vapor–liquid phase equilibrium data were fitted with three thermodynamic models, which corresponded to Wilson, NRTL and UNIQUAC. The parameters of the three activity coefficient models were obtained by the method of nonlinear least-square regression. The calculated vapor–liquid phase equilibrium data with the three activity coefficient models agree very well with the experimental values.

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