Removal of the neutral oil entrained in deep eutectic solvents using an anti-extraction method

Forming deep eutectic solvents (DESs) by quaternary ammonium salts (QASs) and phenolic compounds to extract phenolic compounds from oil mixtures is effective. However, a small amount of neutral oil is entrained in the DESs. In this work, we proposed an anti-extraction method to remove the neutral oil entrained in DESs. Low-carbon alkanes (LCAs, including n -hexane, cyclohexane , and n -nonane) were added to model DESs to remove neutral oil. We found that the LCAs could effectively remove neutral oil entrained in the DESs. Of the three LCAs, n -hexane showed the best performance, and the removal rate of neutral oil could reach as high as 92.2%. The separation process could complete within 15   min, and the removal rate of neutral oil did not change significantly with temperature. In addition, n -hexane could effectively remove neutral oils in DESs formed by real coal tar and choline chloride. The neutral oil content in the phenolic compound product decreased to only 1.9   wt%, which greatly improves the purity of the phenolic compound product.