离子液体液液萃取分离正辛烷/邻二甲苯

将直馏石脑油分离为脂肪烃和芳烃有助于实现石脑油资源的优化利用，溶剂萃取是芳烃/脂肪烃分离的重要途径，萃取剂的设计与优选对萃取过程至关重要。实验探究了多种离子液体对正辛烷/邻二甲苯混合物萃取分离的效果，以萃取选择性、分配系数和萃取性能指数作为评价指标优选出1-丁基-2，3-二甲基咪唑四氯化铁(Bm₂im]FeCl₄])萃取剂。对于中低浓度芳烃体系(<33%)，在30℃、溶剂质量比为4时，邻二甲苯萃取选择性在45以上，分配系数在0.38~0.40，萃取性能指数在18以上，单次萃取脱芳率可达60%以上。相比传统的环丁砜萃取剂，Bm₂im]FeCl₄]萃取剂可以使体系具有更大的两相区，易于正辛烷/邻二甲苯的分离。利用量子化学软件探究Bm₂im]FeCl₄]与正辛烷/邻二甲苯的弱相互作用，并计算其结合能，解释离子液体高选择性萃取邻二甲苯的原因。

Separation of n-octane and o-xylene by liquid-liquid extraction with ionic liquids

Separating straight-run naphtha into aliphatic hydrocarbons and aromatic hydrocarbons helps to optimize the utilization of naphtha resource. Solvent extraction is an important way to separate aromatic hydrocarbons and aliphatic hydrocarbons. The design and optimization of extractants are crucial to the extraction process. The effects of various ionic liquids on the extraction and separation performance of n-octane/o-xylene mixtures were studied, and the ionic liquid 1-butyl-2,3-dimethylimidazole ferric tetrachloride (Bm₂im]FeCl₄]) was selected with extraction selectivity, distribution coefficient and extraction performance index as evaluation indicators. For low and medium concentration of aromatic hydrocarbons in naphtha (<33%), the extraction selectivity of o-xylene was above 45, the distribution coefficient was in the range of 0.38—0.40, the extraction performance index was above 18, and the dearomatization rate of single extraction reached above 60% at the temperature of 30℃ and the mass ratio of solvent to feed of 4. Compared with traditional solvent (sulfolane), the system had a larger two-phase zone with Bm₂im]FeCl₄], which was helpful to separate n-octane and o-xylene. The weak interaction and the binding energy between Bm₂im]FeCl₄] and n-octane/o-xylene were investigated with quantum chemistry software, and the results explained the reason why the ionic liquid could extract o-xylene with high selectivity.