Thermodynamics of amine mixtures. Systems formed by alkyl-amine and ether, or N,N-dialkylamide, or ethanenitrile

TL;DR

This study investigates the thermodynamic behavior of amine mixtures with ethers, amides, and nitriles using literature data and DISQUAC modeling, providing interaction parameters and analyzing enthalpy and phase equilibria.

Contribution

It introduces new interaction parameters for amine/polar compound contacts and demonstrates DISQUAC's effectiveness in describing mixture thermodynamics compared to UNIFAC.

Findings

DISQUAC accurately models excess molar enthalpies and phase equilibria.

Interaction strengths vary with compound type, stronger in N,N-dialkylamides and ethanenitrile.

Structural and orientational effects influence mixture thermodynamics.

Abstract

Systems of the type linear primary or secondary amine + cyclohexane, or + polar compound (namely, linear or cyclic monoether, + 1,4-dioxane, + N,N-dialkylamide, or + ethanitrile) have been investigated using literature data, and by means of DISQUAC. Interaction parameters for the contacts amine/ether, amine/amide and amine/nitrile are provided. For a given contact, the QUAC interchange coefficients remain practically constant along each homologous series. A similar trend has been encountered in other many previous studies. DISQUAC correctly describes excess molar enthalpies, $H_{\text{m}}^{\text{E}}$, and vapour-liquid and solid-liquid equilibria of the studied mixtures and improves calculations on $H_{\text{m}}^{\text{E}}$ from the UNIFAC (Dortmund) model. The experimental data have been used to determine the enthalpy of the interactions between unlike molecules, which are stronger in systems with N,N-dialkylamides or ethanenitrile than in mixtures with ethers. On the other hand, it is shown that $H_{\text{m}}^{\text{E}}$ values of amine + C$_6$H$_{12}$ mixtures are closely related to the amine self-association, and that interactions between molecules of the polar compounds are determinant on $H_{\text{m}}^{\text{E}}$ results of the mixtures amine + fixed polar compound or of the systems fixed amine + polar compound (no linear monoether). Structural effects are relevant in the di-n-butylamine + linear ether systems. The application of the Flory model reveals that orientational effects are rather weak in the investigated solutions. This is in agreement with previous studies on this type of mixtures using the ERAS model.