Effects of different hydrogen bond donors on the extraction of gasoline additive ethanol using deep eutectic solvents formed by choline chloride and dihydric alcohol or dicarboxylic acid as extractant

Ethanol is a common fuel additive, which can significantly improve the quality of fuel. In this work, the sepa-ration effect of n-heptane/ethanol system was explored for the first time by using different dihydric alcohol/ dicarboxylic acid as H-Bond donor choline based deep eutectic solvents. The x-y phase diagrams of n-heptane/ ethanol system with different solvents as entrainers were obtained by experiment. With the carbon chain of H -Bond donors getting longer, the separation effect of solvents on the separation system is better. The contribution of different H-Bond donors to the separation of n-heptane/ethanol system and their intermolecular interactions were explored by molecular simulations. This is because the interaction between solvents and ethanol increases with the growth of H-Bond donor carbon chain. However, the attraction of solvents to n-heptane has been very weak, and has not increased with the increase of H-Bond donor carbon chain. The extractive distillation sepa-ration process with solvents as extractant was developed, which proved that it was feasible to extract ethanol from n-heptane using deep eutectic solvents. This study provides a new idea for the recovery of fuel oil additive ethanol, and provides guidance for the development of new deep eutectic solvents.

Automated summary

In this study, the separation effect of the n-heptane/ethanol system was investigated using different dihydric alcohol/dicarboxylic acid as H-Bond donors in choline-based deep eutectic solvents. Experimentally obtained x-y phase diagrams showed that the separation effect improved with longer carbon chains of H-Bond donors. Molecular simulations explored the contributions of different H-Bond donors and their interactions with the separation system. The study also developed an extractive distillation separation process using deep eutectic solvents, demonstrating the feasibility of extracting ethanol from n-heptane.