Ionic Liquids (ILs) provide an alternative green solvent for separating aromatic from its mixture with aliphatic hydrocarbon. The present work demonstrates the screening of potential IL for separation of benzene (aromatic) from n-hexane (aliphatic) using COSMO-RS. A total of 10 imidazolium based cations and 52 different anions resulting in 520 possible combinations of ILs were studied. The COSMO-RS was used to theoretically calculate the activity coefficient at infinite dilution (γ ∞) for benzene and n-hexane in each of the ILs. Consequently, from the activity coefficient (γ ∞) value, the capacity (C ∞) and selectivity (S ∞) at infinite dilution for each ILs with regards to the benzene/n-heptane separation were calculated. The Performance Index (PI) which is the product of the capacity (C ∞) and selectivity (S ∞) is then determined and compared against sulfolane as the benchmarking solvent, used widely by industry for the separation of benzene and aliphatic hydrocarbon. The result showed 20 ILs with C ∞ , S ∞ , and PI value higher than sulfolane thus making them as potential candidate for the separation application.