The liquid-liquid equilibria between coal tar absorption oil and water have been measured. The distribution coefficients of nitrogen heterocyclic compounds in absorption oil are larger than those of homocyclic compounds. The separation of absorption oil by emulsion liquid membrane is studied. Nitrogen heterocyclic compounds selectively permeate through liquid membrane relative to homocyclic compounds. For the emulsion liquid membrane permeation, the effects of membrane instabilities on the mass transfer rates are found to be so small that the mass transfer rates due to the membrane instabilities are negligible relative to the permeation rates in this study. The stirring rate and surfactant concentration are influential factors for the overall volumetric permeation coefficient and the coefficient increased with these parameters. The separation selectivities of the heterocyclic compounds relative to the homocyclic compounds are sufficiently large. The correlation between the overall volumetric permeation coefficient and distribution coefficient between the feed and membrane phases was obtained, and useful for designing a liquid membrane separation process.