Measurement and correlation of infinite dilution partition coefficients of aromatic compounds in the ionic liquid 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF₆])-CO₂ system at temperatures from 313 to 353 K and at pressures up to 16 MPa

Infinite dilution partition coefficients of benzene, toluene, chlorobenzene and naphthalene in the ionic liquid, 1-butyl-3-methyl-imidazolium hexafluorophosphate ([bmim][PF₆])-CO₂ system were measured with a chromatographic technique. Partition coefficients for each solute increased with increasing pressure and had the trend of K_benzene^∞ > K_toluene^∞ > K_{chlorobenzene}^∞ > K_naphthalene^∞ at a given temperature. At pressures above 12 MPa, K_naphthalene^∞ became one order in magnitude smaller than that of the other components, which is attributed to the π-π interactions between naphthalene and the imidazolium group of the ionic liquid. The Sanchez-Lacombe equation of state was found to provide adequate correlation of the data and their temperature and pressure trends.