Phase equilibria and mechanism analysis of separating ethanol from fuel additives by chord chloride-deep electrochemical solvents

Abstract

There is an azeotropic mixture of ethanol and heptane in the production process of gasoline additives. This work explored the possibility of extracting ethanol from ethanol and heptane with deep eutectic solvents (DESs) to recover components and protect the environment. Three kinds of choline chloride (ChCl)-DESs were synthesized, and then the ternary phase equilibrium data of ethanol, heptane and DESs were measured. The reliability of the data can be verified by the fitting results of the experimental data and the linear equation. In addition, the NRTL model can be correlated with the phase equilibrium results, and the accuracy of the fitted data is determined by the GM/RT surface of GUI-MATLAB. The calculated root mean square deviation shows that the phase equilibrium data has high accuracy. The experimental data show that ChCl-ethylene glycol DES have better ethanol separation results. Then the microscopic mechanism of the separation process was analyzed. The analysis results of electrostatic potential and independent gradient model show that the interaction between DESs and ethanol is mainly hydrogen bond interaction and van der Waals interaction, among which hydrogen bond interaction is the main interaction. In addition, the effect of DES structure on ethanol separation was revealed by the microscopic distribution of molecular dynamics simulation. This work provides a theoretical reference for selecting DESs to separate ethanol-heptane azeotrope.