The group-contribution with association equation of state (GCA-EOS) has been applied to represent the phase behavior of binary systems containing either trifluoromethane (R-23) or hexafluoroethane (R-116) with alkanes. The model was successfully fitted to selected literature data, which also formed part of a study into the use of these refrigerants as supercritical fluid extraction solvents. The tuned model was tested against the available experimental data covering the homologous series of C-2 to C-11 alkanes with either R-23 or R-116, at temperatures between 193 and 343 K and at pressures of up to 60 MPa. The tuned model provided accurate predictions of the phase behavior of these systems, including the ability to identify the carbon number of the alkane in the system at which the phase equilibria transformation occurred. The comparison of the model to the experimental data was excellent, with absolute average relative deviations of between 1% and 5% for both pressure and vapor phase compositions.