Liquid-Solid Phase Diagrams of Ternary and Quaternary Organic Carbonates

This work presents the liquid-solid phase diagrams of ternary and quaternary (or quasiternary) organic carbonates calculated using the thermodynamic nonideal solution models for the carbonates in the liquid state and assuming no solubility of one in any other in the solid state. Further, the molecular interaction term in the models was considered for only binary combinations of different molecules but not for ternary or quaternary interactions. The binary interaction parameters used in the calculation of the ternary and quasiternary phase diagrams were obtained by fitting the same models to the measured phase diagrams of binary carbonates. The results showed the ternary and the quasiternary phase diagrams of the carbonates to have the typical topography of a eutectic ternary system, with a liquidus surface formed from three solubility surfaces of the components which expand in composition and fall in temperature from the melting points of the components. They also showed the effectiveness of adding a carbonate to increase the solubility of another whose cyclicity is the same as that of the added, be it a component by itself or in a mixture, as compared to one with the opposite cyclicity.