Modeling the fluid phase behavior of amines, aromatic amines and their mixtures using the modified group-contribution PC-SAFT

Wertheim’s Association Theory for Phase Equilibrium Modeling in Chemical Engineering Practice

“…The alcohol activity coefficient must exhibit a minimum at the same composition where the amine exhibits a maximum to satisfy the Gibbs–Duhem relation. This behavior can lead to double azeotropy for the diethylamine–methanol mixture , shown in Figure using SPEADMD and NRTL-PA. For SPEADMD, the pure species vapor pressures were corrected to the experimental values. NguyenHuyhn and Nguyen-Thi have also shown that such maxima can be modeled using the mg-SAFT EOS.…”

“…This behavior can lead to double azeotropy for the diethylamine–methanol mixture , shown in Figure using SPEADMD and NRTL-PA. For SPEADMD, the pure species vapor pressures were corrected to the experimental values. NguyenHuyhn and Nguyen-Thi have also shown that such maxima can be modeled using the mg-SAFT EOS. Note in Figure how the positive and negative deviations cancel to result in activity coefficients with maxima and minima but, overall, almost an ideal solution.…”

“…Predictive methods are available for SAFT using group contributions. 117,214,215 For example, Elliott and Natarajan 216 have recommended association energies for the ESD EOS of 16.75 kJ/mol for hydroxyl groups and 5.233 kJ/mol for amines, amides, nitriles, and aldehydes. When the ESD EOS is applied with the association term written in the Wertheim form, Δ = g ESD K AD [exp(ε AD /kT) − 1], where g ESD = 1/(1−1.9b ESD ρ).…”

“…On the contrary, it is possible to formulate rules for the association parameters that are quite intuitive and well-supported by spectroscopic measurements as well as phase behavior. Predictive methods are available for SAFT using group contributions. ,, For example, Elliott and Natarajan have recommended association energies for the ESD EOS of 16.75 kJ/mol for hydroxyl groups and 5.233 kJ/mol for amines, amides, nitriles, and aldehydes. When the ESD EOS is applied with the association term written in the Wertheim form, Δ = g ESD K AD [exp­( ε AD / kT ) – 1], where g ESD = 1/(1–1.9 b ESD ρ ).…”

“…The figure includes some association constants regressed using only experimental mixture data and some regressed from pure component data only. Regression of pure component density and vapor pressure data is insufficient to clearly discriminate between the physical and chemical parameters that are both “sticky”. , Some mixture data are best included to regress the parameters especially if the systems include LLE . Pure component data provide insight using only temperature to vary density, whereas mixture data provide a wider range of density variation.…”