Patent ID: 7078580

Claim:
A composite solvent for separating aromatics from hydrocarbon mixtures by extractive distillation consisting of a main solvent, a solutizer and a modifier; wherein said solutizer is a mixture of any two of C 8 –C 11 aromatics having different numbers of carbon atoms, the content of which is 3–39 wt %, the number of carbon atoms of the aromatic with the lower carbon atom number in the solutizer being greater than that of the aromatic with the highest carbon atom number in the aromatics to be separated, the composite contains 0–10 wt % of the modifier, said main solvent and modifier are independently selected from the group consisting of sulfolane derivatives, N-formyl morpholine, and N-methyl pyrrolidone, provided that the acidity and basicity of the modifier are opposite to those of the main solvent, and said derivatives have the following formula wherein, each of R1, R2, R3, R4 is independently selected from the group consisting of H, C 8 –C 10 alkyl, C 7 –C 12 arylalkyl, C 1 –C 8 alkoxy.