Efficient separation of phenolic compounds from model oils by dual-functionalized ionic liquids

Abstract

Four kinds of dual-functionalized ionic liquids (DFILs, [Et2NEmim][Cl]2, [Et2NEmmor][Cl]2, [Et2NEmpyr][Cl]2 and [Et2NEmpic][Cl]2) were synthesized and used to efficiently separate phenolic compounds from model oils. The effects of stirring time, temperature, mole ratio of DFIL to phenol and initial phenol content on the separation were investigated. The results indicate that at a DFIL:phenol mole ratio of 0.3, the content of phenol in the oil phase can reach the minimum value and the extraction efficiency of phenol is more than 96%. The minimum phenol content in the oil phase and the best phenol extraction efficiency were 5.9 g/m3 and 98.5%, respectively, when [Et2NEmpyr][Cl]2 was used. Compared with traditional ionic liquids, these DFILs not only reduce the dosage of extraction agents but also greatly decrease the content of Cl− in the oil phase due to the double anion in the DFILs. The DFILs can be reused for 4 cycles without losses in phenol extraction efficiency and masses of the DFILs. The separation mechanism of extraction was studied using FT-IR. The result indicates that the two anions Cl− on DFILs can form a hydrogen bond with phenol.