Composite solvent comprising a sulfolane derivative, N-formylmorpholine or N-methylpyrrolidone, amp; C8-11 aromatic for use in extractive distillation

摘要

A composite solvent, for separating aromatics from hydrocarbon mixtures by extractive distillation, comprises a main solvent, 3-39wt% of a solutizer and conditionally a modifier, wherein SL LI(a) the solutizer is selected from any one of C8-C11 aromatics and the composite solvent contains from 0.01 to 10.0 wt% of a modifier, or LI(b) the solutizer is selected from mixtures of any two of C8-C11 aromatics having different numbers of carbon atoms and the composite solvent contains from 0 to 10.0wt% of a modifier, /SL and wherein one of the main solvent and modifier is a sulfolane derivative, and the other is N-formyl morpholine, or N-methyl pyrrolidone, and the sulfolane derivatives have the following formula: EMI ID=1.1 HE=33 WI=42 LX=806 LY=1168 TI=CF PCwherein each of R1, R2, R3 and R4 is independently selected from H, C1-C10 alkyl, C7-C12 arylalkyl and C1-C8 alkoxy. 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 composite solvent is used to recover aromatics by extractive distillation, moderate operating conditions may be used to recover the solvent, and a higher yield of aromatics is obtained. By using a modifier whose acidity-basicity balance is opposite to that of the main solvent, the separated aromatics that are obtained are pH neutral. The use of water in the composite solvent or the extractive distillation process is avoided.