LAUSR

Abstract The extraction of aromatics from aliphatics with both high distribution coefficient (D) and high selectivity (S) is a challenge in the industry. Hydrophobic dicationic ionic liquids (DILs) were demonstrated as efficient extractants with both high D and high S. However, the high viscosity of the DILs may influence their application. In this work, we found that a hydrophobic DIL ([C5(MIM)2][NTf2]2) could dissolve a small amount of water with a solubility of 2.24 wt% at 303.15 K. The viscosity and density of the DIL with different contents of water were investigated from 293.15 K to 333.15 K. A small amount of water in the DIL could decrease its viscosity greatly, while had little effect on its density. The effect of water content in the DIL on the extraction performance was studied, and it was found that both D and S remained high when a small amount of water dissolved in the DIL. The highest selectivity and distribution coefficient for toluene were 45.7, 0.86 (water content: 1.10 wt%) and 41.5, 0.75 (water content: 1.59 wt%), respectively. With increasing the carbon chain of aliphatics, both Dtol and Dali decreased, but S increased in the presence of water. All the results indicated that the DIL with a small amount of water not only had high D and S simultaneously, but also enhanced the extraction process. Importantly, the use of water in the extraction process accords with the concept of green chemistry.