Isobaric (vapor + liquid) equilibrium for n-propyl acetate with 1-butanol or 2-butanol. Binary mixtures at 0.15 and 0.6 MPa

• Vapor pressures of propyl acetate, 1-butanol and 2-butanol were measured from 0 to 1.6 MPa.
• (Vapor + liquid) equilibria of n-propyl acetate with 1-butanol at 0.1, 0.15 and 0.6 MPa as well as n-propyl acetate with 2-butanol at 0.15 and 0.6 MPa were investigated.
• Data were verified with the point-to-point test. All the systems of this paper showed positive consistency.
• Analysis of VLE data reveals that two binary systems (n-propyl acetate + 1-butanol and n-propyl acetate + 2-butanol) have a minimum boiling azeotrope at 0.15 MPa. The n-propyl acetate + 1-butanol presented another azeotrope at 0.6 MPa but no azeotrope was found at 0.6 MPa for the n-propyl acetate + 2-butanol system.
• Several thermodynamics–mathematical equations and activity coefficient models were used to correlate the experimental data.
• The ASOG and three versions of UNIFAC group contribution models were applied to obtain data predictions.

Vapor pressures of propyl acetate, 1-butanol and 2-butanol and the isobaric (vapor + liquid) equilibrium of n-propyl acetate with 1-butanol at 0.1, 0.15 and 0.6 MPa as well as n-propyl acetate with 2-butanol at 0.15 and 0.6 MPa was investigated using a dynamic stainless steel ebulliometer. The experimental data for the binary systems were tested and verified to be thermodynamically consistent by the point-to-point test of Van Ness. Different thermodynamic–mathematical equations together with several activity coefficient models were used to correlate the experimental data. The average absolute deviations for the vapor phase compositions are all below 0.01. In addition, the ASOG and three versions of UNIFAC group contribution models were used to estimate the (vapor + liquid) equilibrium data. The UNIFAC-Dortmund globally generated the best predictions. The mean error in the activity coefficient was less than 7%. For the n-propyl acetate (1) + 1-butanol (2) system an azeotrope has been verified at 0.15 MPa (x1azexp = y1azexp = 0.949 and Tazexp = 387.61 K) and at 0.6 MPa (x1azexp = y1azexp = 0.783 and Tazexp = 445.68 K) while for the n-propyl acetate (1) + 2-butanol (2) system, the azeotrope at 0.15 MPa was found at x1azexp = y1azexp = 0.331 and Tazexp = 383.03 K and was not detected at 0.6 MPa.