Extractive distillation is an alternative for processes where normal distillation is difficult, such as separation of close-boiling mixtures, but solvent selection for distillation is laborious, and its selection pool is narrow. An innovative selection process using molecular simulation is proposed, and the performance of the selected solvent, 1,2,4-trichlorobenzene, for the separation of 1,2,4-trimethylbenzene from a C9 mixture is reviewed. The proposed process requires less investment and leads to lower operating expenses than the conventional two-column process. The computed vapor-liquid equilibrium determined from the molecular simulation is close to the HYSYS estimation in two ternary systems.