Process for separating aromatics by extractive distillation and a composite solvent used therein

摘要

This application relates to a composite solvent for separating aromatics by extractive distillation, comprising a main solvent, a solutizer and a modifier. Said solutizer is selected from any one or mixtures of any two of C₈-C₁₁ aromatics having different number of carbon atoms, the content of which is 3-39 wt %, and the number of carbon atoms of the lowest aromatic in the solutizer should be greater than that of the highest aromatic in the aromatics to be separated. When the solutizer is selected from any one of C₈-C₁₁ aromatics, the composite solvent contains 0.01-10.0 wt % of the modifier; when the solutizer is selected from mixtures of any two of C₈-C₁₁ aromatics having different number of carbon atoms, the composite solvent contains 0-10.0 wt % of the modifier. Said main solvent and modifier are independently selected from 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. When the composite solvent is used to recover aromatics by extractive distillation, it is possible to moderate the operation conditions of solvent recovery, increase the yield of aromatics, and make the separated aromatics to be neutral.