The new liquid-liquid extraction method for separation of phenolic compounds from coal tar

Phenolic compounds are mainly derived from coal tar, petroleum, and coal liquefaction oil. The traditional acid-base separation method can cause serious environmental problems. In this research, imidazole and its homolog compounds were designed as new extraction agents for the separation of phenols from coal tar, which can form deep eutectic solvent with phenols with the removal efficiencies more than 90%. The influence of the extraction agent structure was explored, and different substitutes were investigated. The key experimental conditions, such as reaction time, reaction temperature, and mole ratio of extraction agent to phenols were studied. The hydrogen bond between phenols and extraction agent is the reason for the formation of DES, and this was proved based on analyzing the chemical bonds of product by using FT-IR. The extraction agents exhibited good recycling property. Finally, the experimental process was simulated by Aspen Plus, and a specific separation process and technology was proposed.