Abstract: Using simulated straight-run diesel as feedstock, several solvents were screened for the most appropriate extracting agent, and the operation conditions of the extraction process were optimized. Moreover, the impact of stripping agent types, the ratio of stripping agent to solvent, and the ratio of washing water to solvent on the stripping agent process was investigated. The results showed that increasing the ratio of solvent to feed was beneficial to both extraction selectivity and aromatics removal rate, while raising temperature would lead to decrease of selectivity and increase of aromatics removal rate. Increasing the ratio of water to solvent, the ratio of stripping agent to solvent and the temperature of the distillation column pot were beneficial to the purity of the recovered solvent. Under the optimized conditions of solvent/feed ratio of 3.0 and extraction temperature of 60 ℃, 3-methyl sulfoxide (3-SUL) was used to carry out 7-stage countercurrent extraction for straight-run diesel, the mass fraction of aromatics in the raffinate oil reduced to 6.6%, and the removal rate of aromatics reached 78.2%. Under the optimum conditions of 20 ℃, 0.5 mass ratio of stripping agent to solvent and 0.15 mass ratio of water to solvent, cyclopentane was used to carry out a three-stage reverse extraction for the solvent-rich solvent with soluble extractant, the mass fraction of 3-SUL in the recovered solvent was 99.01%.

Key words: straight-run diesel, liquid-liquid extraction, extractant, solvent recovery, aromatics extraction