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A procedure is presented for designing supercritical gas extraction processes using a pure solvent fluid to effect the separation. The necessary conditions for the procedure to be applicable are the existence of crossover behavior and separable crossover pressures in the fluid phase mixture. Data are presented to support the existence of such phenomena in ternary systems, and an actual separation process has been designed and operated based upon the data. For systems exhibiting this behavior, process synthesis principles are developed to illustrate the evolution of a process flowsheet for the separation of a mixture into its pure components.

The analysis in this paper shows the relationship between molecular resolution in supercritical fluid chromatography (SFC), and certain divergent thermodynamic properties of solutes dissolved in near-critical fluids. This divergence is most pronounced in the near-critical regime, leading to the hypothesis that this region provides most promise for heightened molecular resolution, which lies at the heart of analytical and separation technologies.A thermodynamic model for representing capacity factor data in SFC is proposed, spanning a wide density range. The model uses a perturbed hard sphere equation for the fluid phase and lattice concepts for the stationary phase. In addition, data are presented for a number of systems and discussed in terms of the analysis provided. For an isomeric system, the data shows that resolution between species increases with the onset of retrograde behavior, resulting in a distinct maximum point.

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