Highly selective extraction of aromatics from diesel fuel using dual N-containing heterocyclic deep eutectic solvents

Separation of aromatics and alkanes in diesel fuel is significant for its diversified utilization. In this study, a series of dual N-containing heterocyclic deep eutectic solvents (DESs) were designed and synthesized to separate alkanes/aromatics. The optimal DES (2EmimCl:Trtz) was determined to be 1-Ethyl-3-methylimidazole chloride salt (EmimCl) and 1,2,4-triazole (Trtz) with a molar ratio of 2:1. Sulfolane (SUL) was added as a co-extractant with an optimal molar ratio of 3:1. The extractant ([2EmimCl:Trtz]3SUL) was adopted in the model oil containing dodecane and tetraline. The effects of experimental parameters on the extraction performance were studied, and under optimal conditions, the separation factor for tetraline reached 145.2 with a distribution coefficient of 0.1500. The recycling ability of [2EmimCl:Trtz]3SUL was found to be good. The mechanism of selective extraction was studied using density functional theory (DFT), which indicated that the difference in interaction forces between extractants and aromatics/alkanes is the key to achieving selective separation. Finally, multistage cross-flow extractions of [2EmimCl:Trtz]3SUL were adopted in the six-component model oil and real diesel oil to demonstrate its performance in complex and diesel oil systems.