Molecular mechanism and extraction performance evaluation of ionic liquids for extraction process of n-heptane/n-propanol

Abstract

• The intermolecular hydrogen bond interaction was analyzed based on COSMO-SAC. • The separation mechanism of azeotrope with ILs extractant was studied. • The weak interaction between ILs and n-propanol was analyzed by QC and MD. • The separation process of azeotrope was designed based on the optimal extractant. • The optimal operation parameters were determined by optimization. The use of the n-propanol/n-heptane mixture is known to reduce the content of lead in gasoline. Based on the unique physical and chemical properties of ionic liquids (ILs), such as extremely low volatility, research on the IL-based extraction of azeotropic systems has attracted increasing attention. In this study, experimental results were explained using theoretical analyses. σ-profiles were constructed on the quantum chemistry calculation, and the figure showed that the formation of hydrogen bonds between the ILs and n-propanol was probed. The weak interaction between ILs and n-propanol was qualitatively analyzed using reduced-density-gradient function, electrostatic potential, and bond length analyses. The mechanism by which ILs promoted the separation of the n-propanol/n-heptane azeotropic system was analyzed at the molecular level, thereby providing guidance for the selection of extractants. The liquid–liquid extraction process of n-propanol and n-heptane using [DMIM][MP] as an extractant was established using the Aspen Plus software. The effects of the application of ILs in liquid–liquid extraction was simulated, and the results provided basic data and theoretical references for the practical application of ILs in azeotropic liquid–liquid extraction.