An ionic liquid extraction process for the separation of indole from wash oil
Indole is an important industrial substance derived from wash oil, and the traditional alkali fusion method causes serious environmental problems. In this research, imidazolium-based ionic liquids (IBILs) were developed as new extraction agents to separate indole from wash oil with extraction efficiencies of more than 90%. The influence of the IBIL structure was explored. The extraction efficiency and the distribution coefficient of indole were used as the indexes to evaluate the IBIL extraction ability. The key experimental parameters, such as the initial indole concentration, extraction time, extraction temperature, and volume ratio of IBIL-to-model wash oil, were investigated to obtain the optimum conditions. The separation mechanism was studied by analyzing the chemical bonds using spectrographic analysis and molecular simulations. The IBILs were recycled by back-extraction and they exhibited good recycling properties with no obvious reduction and a high extraction efficiency. Finally, the optimal process was conducted based on the process simulation.