Composite solvent, for separating aromatics from hydrocarbon mixtures by extractive distillation, comprises main solvent and modifier which is sulfolane derivatives, N-formyl morpholine or N-methyl pyrrolidone, and solutizer

摘要

The composite solvent comprises a main solvent, a solutizer and a modifier. The amount of solutizer in the composite solvent is 3-39 wt.% and is selected from 8-11C aromatics. The main solvent and modifier are independently selected from sulfolane derivatives, N-formyl morpholine and N-methyl pyrrolidone. The composite solvent comprises a main solvent, a solutizer and a modifier. The amount of solutizer in the composite solvent is 3-39 wt.% and is selected from any one of mixtures of any two of 8-11C aromatics having different number of carbon atoms. 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 8-11C aromatics, the composite solvent contains 0.01-10 wt.% of the modifier, and when the solutizer is selected from mixtures of any two of 8-11C aromatics having different number of carbon atoms, the composite solvent contains 0-10 wt.% of the modifier. The main solvent and modifier are independently selected from sulfolane derivatives, having formula (I), N-formyl morpholine and N-methyl pyrrolidone, provided that the acidity and basicity of the modifier are opposite to those of the main solvent. R1-R4 = hydrogen, 1-10C alkyl, 7-12C arylalkyl or 1-8C alkoxy. An Independent claim is included for separating aromatics from hydrocarbon mixtures. The composite solvents are introduced to the upper portion of an extractive distillation column and hydrocarbon mixture is introduced to the middle of the column. The non-aromatics are withdrawn from the top of the extractive distillation column. Rich solvent containing aromatics is introduced from the bottom of the distillation column to the middle of solvent recovery column to separate aromatics and the composite solvent. The aromatics obtained from the top of the recovery column are withdrawn and composite solvent withdrawn from the bottom of the solvent recovery column is introduced into the top of the extractive distillation column for recycling. Thus, aromatics are separated from the hydrocarbon mixture.