Ionic liquids design for efficient separation of anthracene and carbazole

Anthracene (ANT) and carbazole (CAR) are highly value-added compounds in chemical industry. They are always mixed in preliminary processing products of high temperature coal tar and need to be separated and purified. In this study, ionic liquids (ILs) were used to separate ANT and CAR. [C3PY], [PM2IM] and [PMPIP] cations along with 7 classes of anions were screened by the conductor-like screening model for real solvents (COSMO-RS). [PMPIP][TFAc] (ILa) and [PMPIP][Ac] (ILb) were selected and synthesized. The structures of ILs were studied by σ-profile at the micro-level to analysis the hydrogen bonds formed between anion of ILs and H-N of CAR. The ternary phase diagrams of ANT-CAR-ILs were plotted to analysis the separation efficiency. Two ILs were used as extractant to separate ANT and CAR. The separation results showed that the synthesized ILs were the highly efficient solvents. The purity of refined ANT separated by ILb was improved to 97.87 wt%, with a yield of 80.04 wt%. The separation mechanism of ANT and CAR was further discussed.