Studies on phase equilibria of a multicomponent model mixture in supercritical carbon dioxide and trifluoromethane

Abstract

Phase equilibria were studied of a multicomponent model mixture representing the middle distillate of a coal liquefaction product in the gases carbon dioxide and trifluoromethane at temperatures (308–338 K) and pressures (6–30 MPa) above the critical points of the gases. Partition coefficients and separation factors were determined for the individual mixture components by analysing samples from the coexisting phases. The results show that selectivity due to structural properties (π-bonds, dipole moments, etc.) is superimposed by selectivity due to differences in vapor pressures. The concepts of structure selectivity and vapor pressure selectivity are introduced and changes of these parameters with pressure and temperature are reported. Enhancement factors in the carbon dioxide/model mixture system were calculated and show good agreement with the experimental results.