Deterpenation of tea tree oil by liquid-liquid extraction with hexalkylguanidinium ionic liquid

[Display omitted] •Extractive deterpenation of model tea tree oil (MTTO) was performed by ILs.•Five ILs were prepared after screening via density functional theory (DFT).•Hexalkylguanidinium ionic liquid had high extraction performance.•Post treatment with n-hexane benefited deep deterpenation of MTTO. Terpinen-4-ol in natural Tea tree oil (TTO) plays an important role in physiological activities. Selectively removing of 1,8-cineole and the monoterpenes such as γ-terpinene from TTO is necessary for TTO comfort and safety. In this study, the density functional theory (DFT) was employed to estimate the interaction energies between ILs and terpinen-4-ol for preliminarily screening ionic liquid type of extraction agents. It was found hexalkylguanidinium ionic liquids (ILs) [diBTMG]Br exhibited good extraction distribution coefficient of terpinen-4-ol (2.54) and higher extraction selectivity of terpinen-4-ol (6.9 to 1,8-cineole and 9 to γ-terpinene, respectively). The single extraction yield of terpinen-4-ol by the IL could reach to 90%. After the extraction, subsequent twice extractions with n-hexane and water can realize satisfactorily recovery and reuse of all extraction agents. The deterpenation of TTO has advantages of lower energy consumption, safety, environmentally friendly and less cost. It would provide an alternative strategy for the practical deterpenation production of essential oil with ionic liquids.