Separation of anthracene and carbazole from crude anthracene via imidazolium-based ionic liquids

Anthracene and carbazole, the main components of crude anthracene, have high added value in chemical industry. In this study, two imidazolium-based ILs, [PM2IM][TFAc] (ILa) and [PM2IM][Ac] (ILb), were synthesized to separate anthracene and carbazole. The effective separation of anthracene and carbazole was achieved by hydrogen bonding between carbazole and imidazolium-based ILs. The results of density functional theory simulation and 1H NMR verification showed that the hydrogen bond interaction between carbazole and ILs was via CO…HN, and the hydrogen bond strength between ILb and carbazole was stronger than that of ILa. Based on the process for the separation of anthracene and carbazole from crude anthracene by imidazolium-based ILs, the purity of refining anthracene reached 94.89% and that of crude carbazole reached 81.60%. In addition, this process test realized recovery and recycling of ILs.