Equilibrium tie line data have been determined for the two ternary liquid systems: I tetradecane, or heptadecane + pentylbenzene + N-methyl-2-pyrrolidone (NMP)) over a temperature range of (298 to 328) K. The two systems studied exhibit type I liquid + liquid phase diagram. The effect of temperature and n-alkane chain length upon solubility, selectivity, and distribution coefficients were investigated experimentally. (C) 2005 Published by Elsevier Ltd.