Evolution of the Liquid–Vapor Equilibrium Properties of Several Unsymmetrical Amines: Determination of Their Binary Isobaric Diagrams and Applications to the Distillation

This work deals with the synthesis, extraction, and purification of a new exocyclic hydrazine with cosmetic applications, N-aminopyrrolidine (NAPY). The final extraction and purification steps of the useful product are often linked to distillation operations. The optimization of these separation conditions requires then the knowledge of the thermodynamic properties of the liquid–vapor equilibria. The synthesis reactions are carried out by the Raschig process, which is based on the reaction of a large excess of amine with chloramine in aqueous medium and without any use of solvent. The distillation step involves the liquid–vapor equilibria in the ternary system NAPY + pyrrolidine + water and, first of all, requires the knowledge of the water + pyrrolidine binary system. For a better understanding of the behavior of aqueous mixtures of amine, three liquid–vapor binary diagrams of water + amine type were investigated by ebulliometry. The three binary isobaric diagrams water + pyrrolidine, water + butylamine, and water + diethylamine were established under atmospheric pressure. The evolution of the thermodynamic properties of these amines according to the nature of the substituent will be then deduced by comparison of these experimental diagrams. This study will thus lead us to a better understanding of the molecular interactions in the liquid phase.