Selection of deep eutectic solvents for extractive deterpenation of lemon essential oil

Lemon essential oil is a complex mixture with citral as the primary terpenoid and limonene as the main terpene. Isolation of terpene and terpenoid, known as deterpenation, is crucial for improving the essential oil quality. In this work, liquid–liquid extraction with deep eutectic solvents (DESs) is utilized for lemon essential oil deterpenation. The performance of 77 DESs formed by seven hydrogen bond acceptors (HBA) with eleven hydrogen bond donors (HBD) is evaluated using COSMO-RS model and verified experimentally. The influences of HBA and HBD structures are investigated and explained by σ-profile. Among 77 DESs, the DES composed of tetrabutylammonium bromide and levulinic acid, namely TBAB:LEA(1:2), is finally selected due to its better performance than the conventional solvent hydrous ethanol. The excellent performance of TBAB:LEA(1:2) in deterpenation of natural lemon essential oil suggests it is a promising solvent in the downstream processing of natural essential oil.