Binary systems containing supercritical CO₂ + hydrocarbons were used for modeling gas–solid equilibrium by a combined method including a thermodynamic model and a meta-heuristic algorithm. The Peng–Robinson (PR) equation of state was used in the classical solubility equation. In addition, Wong–Sandler (WS) mixing rules were used, and the van Laar model (VL) was included in order to evaluate the excess Gibbs free energy that appears in these mixing rules. Then, a variant of particle swarm optimization (PSO), called Frankenstein PSO (FPSO) was implemented for minimizing the difference between calculated and experimental solubility values. The results showed that the FPSO algorithm is a very powerful tool for parameter estimation on the PR-WS-VL model with good performance and accuracy, and considerably low deviations. Therefore, values calculated by the combined method (PR-WS-VL + FPSO) are considered accurate enough for physical and engineering calculations, among other uses.