The use of high pressure NMR for the determination of phase behavior for select binary solvent systems

High pressure NMR has proven itself to be a valuable technique for the study of supercritical fluid solutions. In this manuscript, we describe the extension of high pressure NMR to the investigation of the phase behavior for two binary solvent systems; ethylene-methanol and propane-methanol. The phase behavior was investigated as a function of pressure and temperature, with the molar composition of both phases being determined simultaneously, in situ, in a high pressure capillary NMR cell. The hydrogen bonding behavior of the alcohol in both phases determined in these experiments, provides important physicochemical information regarding solvent interactions occurring in both the liquid and vapor phase. High pressure NMR proves to be an efficient method for obtaining vapor liquid equilibrium data and critical conditions of binary solvent systems. This methodology should also be applicable to ternary systems as well as to more extreme solvent systems, such as, supercritical water.