TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Material: The first hydrocarbon is aromatic hydrocarbons, cycloalkanes, cycloalkenes, cycloalkenes and/or cycloalkadienes.The aromatic hydrocarbons contain 6-10C/molecule.The closed-boiling second hydrocarbon is alkanes, alkenes and/or alkadienes.It is preferably pentane; 2-methylbutane; hexane; 2,2-diemthylbutane; heptane; 2,2,3-triemthylbutane; 2,2-trimethylbutane; 2,2-diemthylpentane; and/or 2,4-diemthylpentane.The cycloalkanes, cycloalkenes, cycloalkenes, cycloalkadienes, alkanes, alkenes and alkadienes contain 4-10C/molecule.The aromatic hydrocarbons are benzene, toluene, meta-xylene, ortho-xylene, para-xylene, ethylbenzene, trimethylbenzenes and/or methylethylbenzenes.The cycloalkanes are methylcyclopentane, ethylcyclopentane, methylcyclohexane, cyclooctane, dimethylcyclohexanes, ethylcyclohexane, cyclononane, cyclopentane, cyclohexane and/or cycloheptane.The cycloalkenes are cyclopentene, cyclohexene, methylcyclopentenes, cycloheptene, methylcyclohexenes and/or cyclooctene.The cyclodienes are cyclohexadienes, cycloheptadienes, methylcyclohexadienes and/or cyclooctadienes.The alkanes are butane, pentane, methylbutanes, hexane, dimethylbutanes, methylpentanes, heptane, trimethylbutanes, dimethylpentanes, methylhexanes, octane, trimethylpentanes, dimethylhexanes, methylheptanes, nonane, dimethylheptanes and/or decane.The alkenes are pentenes, methyl-1-butenes, methyl-2-butenes, hexenes, dimethylbutenes, methylpentenes, heptenes, methylhexenes, octenes, methylheptenes, nonenes and/or decenes.The alkadienes are butadienes, pentadienes, hexadienes, dimethylbutadienes, methylpentadienes, heptadienes, methylhexadienes, octadienes, nonadienes and/or methyloctadienes.The boiling points of the first and second hydrocarbons are 100-500 degreesC, preferably 100-450 degreesC.Preferred Composition: The hydrocarbon-containing fluid comprises 0.1-99.9 wt.% first hydrocarbon and 0.1-99.9 wt.% second hydrocarbon.Preferred Solvent: The 3-alkyl-substituted-2-oxazolidinone is 3-ethyl-2-oxazolidinone, 3-propyl-2-oxazolidinone and/or 3-butyl-2-oxazolidinone or preferably 3-methyl-2-oxazolidinone.Preferred Ratio: The weight ratio of the solvent/hydrocarbon-containing fluid is 1:1-40:1, preferably 2:1-25:1.Preferred Process: The extractive distillation comprises a reflux ratio in 0.1:1-100:1, hydrocarbon-containing fluid entry location of 2-70% of the total height of the packed or trayed column (12), a solvent entry location of 50-99% of the total height of the packed or trayed column, a reboiler vessel temperature or 200-500 degreesF, and a pressure of 5-100 psig. It produces an overhead distillate product containing a smaller volume percentage of first hydrocarbon and a larger volume percentage of second hydrocarbon; and a bottom product containing solvent and larger volume percentage of first hydrocarbon and smaller volume percentage of second hydrocarbon than the fluid. It also separates the first hydrocarbon from the solvent in the bottom product.