Extraction of Aromatic Hydrocarbons from Aromatic/Aliphatic Mixtures Using Chloroaluminate Room-Temperature Ionic Liquids as Extractants

摘要

The extraction of aromatic hydrocarbons from aromatic/aliphatic mixtures was investigated using chloroaluminate ionic liquids as extractants. Three types of chloroaluminate ionic liquids, i.e., 1-butyl-3-methylimidazohum chloride—aluminum chloride (BMIC/AlCl3), trimethylamine hydrochloride— aluminum chloride (Me3NHCl/AlCl3), and triethylamine hydrochloride—aluminum chloride (Et3NHCl/AlCl3), were prepared and used to extract aromatic hydrocarbons. Chloroaluminate ionic liquids have strong aromatic hydrocarbon solvent capacities, small solvent capacities for n-heptane, and good extractive performances. BMIC-2.0AlCl3 exhibits better extractive performance than Me3NHCl-2.0AlCl3 and Et3NHCl-2.0AlCl3. Both the benzene distribution coefficient and aromatic/n-heptane selectivity increase with an increasing ratio of AlCl3/organic salt (Et3NHCl) in ionic liquids. The steric effect of substituent groups on the benzene ring lowers the aromatic extractive performance. The pi complextion between aromatic molecules with highly delocalized pi electron and Lewis acid species (Al2Cl_7~- or AlCl3) facilitates the aromatic absorption of chloroaluminate ionic liquids. A lower temperature is favorable for aromatic extraction of the ionic liquids. The regeneration tests show that the used ionic liquids can be recovered through vacuum distillation effectively.