Fluid Mixtures at High Pressure. Phase Separation and Critical Phenomena in Binary Mixtures of a Polar Component with Supercritical Carbon Dioxide, Ethane, and Ethene up to 1000 Bar.

Abstract

AbstractIn order to study the polarity effect on the critical phase behaviour of fluid binary systems the critical temperatures of binary mixtures of carbon dioxide, ethane, ethene, hexane, or 1‐hexene with a second component of very different polarity such as methanol, 2‐hexanol, 2‐octanol, 2,5‐hexanediol, nitromethane, N,N‐dimethylformamide, or N‐methylacetamide were determined as a function of pressure up to 1000 bar. The critical p(T) curves obtained exhibit a whole pattern of different transition types between liquid‐gas, liquid‐liquid, and gas‐gas equilibria; they are compared with data for other systems taken from the literature.The results verify a previous hypothesis that there are continuous transitions between liquid‐gas, liquid‐liquid, and gas‐gas critical phenomena in fluid binary mixtures at high pressures. The measurements are of interest for fluid extraction and supercritical fluid chromatography (SFC).