Ionic liquids are suitable candidates for green extraction processes as they have very low vapor pressure. COSMO-RS, a general and fast method for the prediction of thermophysical data of liquids, is used for the calculation of solution properties of toluene and heptane in more than a thousand ionic liquid solvents. The ionic liquid database contains about thirty anions and fifty cations based mainly on pyrrolidinium, imidazolium and pyridinium. Selectivities and capacities are determined for toluene-heptane separation for all the ionic liquids .Some of the data have been compared with experimental values. Finally some ionic liquids have been recommended for aromatic extraction from aromatic-aliphatic mixture.